This paper characterises optimal monetary policy in an economy with endogenous firm entry, a cash-in-advance constraint and preset wages. Firms must make pro fits to cover entry costs; thus the markup on goods prices is efficient. However, because leisure is not priced at a markup, the consumption-leisure tradeoff is distorted. Consequently, the real wage, hours and production are suboptimally low. Due to the labour requirement in entry, insufficient labour supply also implies that entry is too low. The paper shows that in the absence of fiscal instruments such as labour income subsidies, the optimal monetary policy under sticky wages achieves higher welfare than under flexible wages. The policy maker uses the money supply instrument to raise the real wage - the cost of leisure - above its flexible-wage level, in response to expansionary shocks to productivity and entry costs. This raises labour supply, expanding production and rm entry.