Using data collected with the BESIII detector in e + e − collisions at center-ofmass energies between 4.178 and 4.226 GeV and corresponding to 6.32 fb −1 of integrated luminosity, we report the amplitude analysis and branching-fraction measurement of the D + s → π + π 0 η decay. We find that the dominant intermediate process is D + s → ρ + η and the significances of other resonant and nonresonant processes are all less than 3σ. The upper limits on the branching fractions of S-wave and P -wave nonresonant components are set to 0.10% and 0.74% at the 90% confidence level, respectively. In addition, the branching fraction of the D + s → π + π 0 η decay is measured to be (6.15 ± 0.25(stat.) ± 0.18(syst.))%, which receives significant contribution only from D + s → ρ + η according to the amplitude analysis.