Olaparib is a widely used PARP inhibitor for the treatment of BRCA-mutated cancers. To comprehensively understand the drug's clinical impact, measuring its interactions with intended on- and off-targets is crucial. In this study, olaparib's on- and off-targets were profiled using photoaffinity labeling, a powerful, proteome-wide method for studying the direct interactions between a drug and its protein targets. A novel photoaffinity probe was designed and used in a proteomic screening to discover novel targets of olaparib in the human proteome. The probe, incorporating a pre-installed biotin group, bypasses the limitations of using a copper(I)-catalyzed click reaction in cell lysates for reporter group conjugation and revealed a broad range of olaparib interactors, including previously unreported proteins, in a quantitative mass spectrometry-based proteomic screening using HeLa whole cell lysate. This study contributes to our current understanding of the pharmacology of olaparib and provides a valuable tool for elucidating drug interactors within cell lysates, potentially guiding the development of more targeted therapeutics with fewer off-targets.