This paper introduces collective bargaining at the firm and at the sector level into the heterogeneous firm model of Melitz and Ottaviano (Melitz, M. J., Ottaviano, G. I. P., 2008. Market size, trade, and productivity. Review of Economic Studies 75(1), 295-316). It then analyses how the two bargaining regimes change aggregate industry productivity and firm performance relative to a competitive labour market. While sector-level bargaining forces the least productive firms to exit and thus increases average productivity relative to the competitive benchmark, firm-level bargaining allows less productive firms to stay in the market and thus reduces average productivity. Sector-level bargaining also results in higher average output and profit levels than either firm-level bargaining or a competitive labour market. The paper also shows that the choice between sector- and firm-level bargaining can involve a trade-off between product variety and product prices: Not only the average price level but also product variety tends to be lower under sector-level bargaining than under firm-level bargaining.