Thalidomide and its derivatives lenalidomide and pomalidomide (IMiDs) are effective treatments of hematologic malignancies. It was shown that IMiDs impart gain of function properties to the CUL4-RBX1-DDB1-CRBN (CRL4CRBN) ubiquitin ligase that enable binding, ubiquitination and degradation of key therapeutic targets such as IKFZ1, IKZF3 and CSNK1A1. While these substrates have been implicated as efficacy targets in multiple myeloma (MM) and 5q deletion associated myelodysplastic syndrome (del(5q)-MDS), other targets likely exist. Using a pulse-chase SILAC mass spectrometry-based proteomics approach, here we demonstrate that lenalidomide induces the ubiquitination and degradation of ZFP91. We establish that ZFP91 is a bona fide IMiD dependent CRL4CRBN substrate and further show that ZFP91 harbors a zinc finger (ZnF) motif, related to the IKZF1/3 ZnF, critical for IMiD dependent CRBN binding. These findings demonstrate that single time point pulse-chase SILAC mass spectrometry-based proteomics (pSILAC-MS) is a sensitive approach for target identification of small molecules inducing selective protein degradation.