Unitranche vs First Lien vs Mezzanine: What the Structure Actually Changes

"Walk me through unitranche versus first lien versus mezzanine" is the standard comparison question in a private credit interview, and a candidate who answers with a ranking, senior, blended, junior, has stated an order without explaining what it changes. The stronger answer works through what that seat in the structure changes for downside protection, control, pricing, and why the borrower chose it in the first place.

Why These Structures Exist in Real Deals

A lot of candidates memorize the ranking and stop there. The more useful question is why a given company ends up in one structure instead of another, because that borrower logic is what an interviewer is actually testing. A borrower picks first lien when it wants the cheapest senior debt and is willing to accept the lender protection that comes with that price. It picks unitranche when speed, one financing package, and certainty of execution matter more than shaving the coupon. It reaches for mezzanine when it wants more leverage than the senior lenders will provide, without writing a bigger equity check.

Structure choice reveals as much about the deal as the leverage multiple.

First Lien: Highest Protection, Lowest Return

First lien debt sits highest in the capital structure, usually with the strongest claim on collateral and the first call on recoveries. Federal Reserve staff who study the asset class note that the share of private credit loans secured by a first lien has kept rising over time, while a smaller slice, hybrid loans that rank pari passu with but behind the senior tranche, held at about 15% of the market as of 2023 [1]. Golub Capital BDC, one of the listed vehicles that originate these loans, put 92% of its own portfolio in first lien senior secured debt as of 30 June 2026, close to what "senior secured" now means at scale [3]. That concentration is the trade-off made visible: first priority on repayment, the strongest security package, and usually the tightest covenant protection, in exchange for the lowest coupon of the three. How covenant packages actually protect that seat is worth knowing before calling first lien automatically the safe answer.

The lowest coupon buys the best downside protection.

Unitranche: One Lender, Blended Risk

Unitranche usually folds what might otherwise be separate senior and junior tranches into one facility, split internally between a first-out piece and a last-out piece rather than across two lender groups. Borrowers like it for the reasons that matter under a tight timeline: one lender group, an Agreement Among Lenders instead of a public intercreditor agreement, one documentation package, and one blended rate to negotiate instead of two. The lender on the other side takes blended risk instead of a clean senior seat, first-out protection on part of the facility and last-out exposure on the rest, which is why unitranche prices above a pure first lien.

Seniority alone does not fully explain how a loan recovers. Federal Reserve estimates put the post-default recovery on private credit loans generally at around 33%, against 52% for syndicated loans and 39% for high-yield bonds, even though private credit has become the more senior-secured of the three markets [1]. More than half of private credit by value goes to borrowers in software, financial services, and other asset-light sectors with little hard collateral to seize [1], which is the piece of the puzzle a clean seniority ranking leaves out. If spread compression in the broadly syndicated loan market continues through 2027, expect some of the unitranche premium over a pure first lien to narrow with it, since part of that premium compensates the last-out lender for giving up the liquidity of a traded loan, not only for taking blended risk.

Unitranche prices for blended risk, not a clean senior seat.

Mezzanine: More Leverage, Weaker Seat, Higher Return

Mezzanine sits below the senior debt and carries materially more loss risk, since it is repaid only from what remains once the senior lender is covered. The Financial Stability Board notes that private credit borrowers overall are often rated around single B- and typically carry more leverage than borrowers in the broadly syndicated loan market [2], and mezzanine is the layer that absorbs the difference when a sponsor wants to push past what a senior lender alone will underwrite. Pricing usually runs well above the senior debt and often blends a cash-pay coupon with a PIK component, which changes what a missed payment actually means for the lender.

Mezzanine is paid more because it relies on enterprise value, not collateral.

The Borrower's Side of the Trade

Most weak answers explain these structures only from the lender's side. The borrower's incentives are what make the ranking useful in an interview, because they explain why a company ends up with one structure rather than another. A sponsor facing a tight process often prefers unitranche precisely because fewer lenders and one document set lower execution risk when the timeline is short. A sponsor that wants to stretch leverage without writing a larger equity check reaches for mezzanine instead, even at a much higher coupon, because the alternative is a smaller deal or a bigger check. The same logic runs through the choice between a direct lender and a syndicated loan: speed and certainty on one side, price and liquidity on the other.

The borrower's constraint, not the lender's preference, usually picks the structure.

The Four-Way Comparison

Four dimensions carry the comparison in an interview: structural position, recovery protection, pricing, and borrower utility.

Unitranche vs First Lien vs Mezzanine — What Actually Differs

	First Lien	Unitranche	Mezzanine
Position in the waterfall	Senior secured	Senior secured, split first-out / last-out	Contractually subordinated
Pricing, relative	Tightest of the three	Above first lien, blended	Highest, often part PIK
Security	First lien on all assets	First lien on all assets	Unsecured, or second lien
Ranking mechanism	Intercreditor agreement	Agreement Among Lenders	Subordination agreement
Visible to the borrower	Yes	No, one agent, one rate	Yes, separate documents
Maintenance covenants	Usually one	Usually one	Set with a cushion to the senior
Execution speed	One senior lender group	Usually fastest, one process	Slower, negotiated alongside the senior
Who takes the first loss	The tranche below it	The last-out lender	The mezzanine lender

Source: Qualitative ranking of terms as customarily documented in US mid-market transactions; not a market survey. Illustrative pricing for a specific deal appears in the Meridian Coatings worked example below.

Borrower utility is the dimension most candidates skip. First lien is usually cheapest, unitranche is usually fastest to close, and mezzanine is the lever that lets a sponsor push leverage past what the senior debt alone would support.

Pricing without borrower utility is half the comparison.

Worked Example: Meridian Coatings

Meridian Coatings is the fictitious sponsor-backed industrial coatings manufacturer used across these articles, financed at close with a $40mm revolver and a single unitranche term loan against $45.0mm of LTM EBITDA.

Meridian Coatings — Capital Structure at Close ($ in mm)

Facility	Face Value	Interest Rate	Maturity	xEBITDA
$40mm Revolver (drawn)	$10.0	S + 4.75%	Mar-29
Unitranche Term Loan	202.5	S + 5.50%	Mar-31
Total Debt	$212.5			4.7x
Less: Cash and Equivalents	(12.5)
Net Debt	$200.0			4.4x
Memo — LTM EBITDA $45.0 / Undrawn Revolver $30.0 / Total Liquidity $42.5 / Sponsor Equity $178.0

Source: Illustrative. Computed on the Meridian Coatings worked example; not drawn from any real transaction.

The unitranche term loan prices at S + 5.50% on the full $202.5mm. A split structure covering the same $212.5mm of total debt, a $150.0mm first lien at S + 4.00% and a $52.5mm mezzanine tranche at a fixed 11.00%, part PIK, would have carried a lower blended cash coupon at the same illustrative base rate, at the cost of two lender groups instead of one, ranked against each other by an Agreement Among Lenders or a subordination agreement rather than a single credit agreement.

Meridian Coatings: Unitranche vs a Split First Lien / Mezzanine Structure ($ in mm, illustrative)

Facility	As Financed: Unitranche	Alternative: Split Structure
$40mm Revolver (drawn)	$10.0	$10.0
First Lien Term Loan	–	$150.0
Unitranche Term Loan	$202.5	–
Mezzanine / Subordinated	–	$52.5
Total Debt	$212.5	$212.5
xEBITDA	4.7x	4.7x
Lender groups	One	Two, ranked by an Agreement Among Lenders or a subordination agreement
Illustrative blended cash coupon*	9.50%	8.78%

*At an illustrative SOFR of 4.00%: unitranche priced S + 5.50% on the full $202.5mm. Split structure computed on $150.0mm first lien at S + 4.00% and $52.5mm mezzanine at a fixed 11.00%, part PIK. Illustrative, computed on the Meridian Coatings worked example; not drawn from any real transaction.

The gap between the two columns is the price of simplicity: about seventy basis points of blended coupon, paid to collapse two negotiations, two covenant packages, and two lender relationships into one.

Simplicity has a price, and the split structure shows what it is.

The 45-Second Answer

A tight answer runs about forty-five seconds:

"I would distinguish them by where risk and control sit in the structure. First lien is senior secured debt with the strongest collateral and recovery position, so it usually earns the lowest return. Unitranche blends senior and junior risk into one facility, which gives the borrower speed and simplicity but means the lender wants a higher coupon than on pure first lien debt. Mezzanine is junior to the senior debt, so it relies more on enterprise value and takes more loss risk, which is why pricing is higher."

What Weak Answers Sound Like

Weak answers reduce the comparison to pricing: first lien is cheap, mezzanine is expensive, unitranche sits in between. That is true, and it is not an analysis. The stronger version names four things:

• where the lender sits in the structure
• what protection that seat provides
• why the return differs
• why the borrower chose that structure in the first place

Naming the trade-off, not the ranking, is the analysis.

The distinction that matters runs deeper than senior, blended, junior: structural seat, recovery protection, control, and how each is priced, because that is what turns a memorized ranking into credit judgment. The free credit investment memo framework is built to practice exactly this kind of distinction in a case-study format: what matters, what breaks, and whether the structure compensates the lender enough to hold the paper. The private credit interview guide covers where this comparison sits inside the wider process, alongside the case study and the rest of the technicals. For the full prep stack, 80 Q&As, case-study drills, cheat sheets, and the deal memo framework, see the Interview Guide.

Sources and Method

Figures marked illustrative are computed on the Meridian Coatings worked example and are not drawn from any real transaction. All market figures are reported as of the date shown in the source and were last verified on 2026-07-29.

[1] Fang Cai and Sharjil Haque, "Private Credit: Characteristics and Risks", FEDS Notes, Board of Governors of the Federal Reserve System, 23 February 2024. https://www.federalreserve.gov/econres/notes/feds-notes/private-credit-characteristics-and-risks-20240223.html [2] Financial Stability Board, "Report on Vulnerabilities in Private Credit", 6 May 2026. https://www.fsb.org/uploads/P060526.pdf [3] Golub Capital BDC, Inc., "GBDC at a Glance", investor relations website, data as of 30 June 2026. https://www.golubcapitalbdc.com/