Protein phosphorylation plays a central role in regulating cellular signaling, and its dysregulation is closely linked to diseases such as cancer and neurodegeneration. Mass spectrometry-based phosphoproteomics allows comprehensive mapping of phosphorylation; however, detecting low-abundance and poor ionization phosphopeptides remains a challenge. High-field asymmetric waveform ion mobility spectrometry (FAIMS) offers orthogonal gas-phase fractionation, enhancing phosphopeptide detection. However, FAIMS and conventional non-FAIMS (noFAIMS) analyses often identify partially overlapping yet complementary subsets of phosphopeptides. This suggests that integrating both approaches could significantly increase the depth of phosphoproteomic analysis.