We defined the folding sequence of the fold–thrust belt of the Western Papua New Guinea Highlands by analysing the surface expression of the structures and the response of the drainage system to the active fold–thrust belt. The interaction between structures is typically assessed by examining the syn-kinematic strata preserved; however, in our study area, this is problematic as these strata are poorly imaged on seismic lines. This study found common morphological features that allowed grouping and mapping of three different structural settings: group I, basement-involved tectonics; group II, thin-skinned anticlines which sole near the Koi–Iangi Sandstone; and group III, thin-skinned folds associated with the intra-Ieru Formation detachment. Fold Front Sinuosity analysis supports the idea that the fold–thrust belt propagates from the NW to the SE. Considering the detailed morphotectonics and drainage analyses, we interpret that the group II folds developed as out-of-sequence thrusting and folding, associated with buttressing against the group I larger structures.