Empirical evidence suggests that bank lending rates are downward rigid: banks tend to adjust their rates more slowly and less completely to short-term market rates decreases than to increases. We investigate the macroeconomic consequences of this downward interest rate rigidity by introducing asymmetric bank lending rate adjustment costs in a macrofinance dynamic stochastic general equilibrium model. Calibrating the model to the euro area economy, we find that the difference in the initial response of GDP to positive and negative economic shocks of similar amplitude can reach up to 25%. This means that a central bank would have to cut its policy rate much more to obtain a symmetric medium-run impact on GDP. We also show that downward interest rate rigidity is stronger when policy rates are stuck at their effective lower bound, further disrupting monetary policy transmission. These findings imply that neglecting asymmetry in retail interest rate adjustments may yield misguided monetary policy decisions.