This study, conducted in a centralized cytotoxic drug preparation unit, analyzes the effectiveness of two closed system drug transfer devices (CSTDs) in reducing leakage during antineoplastic drug compounding. Wipe/pad samplings inside and outside the preparation area were taken during surveillance programs from 2016 to 2021. All samples were analyzed for gemcitabine (GEM) contamination. In 2016, the presence of GEM in some samples and the contamination of the operators’ gloves in the absence of apparent drug spilling suggested unsealed preparation systems. In subsequent monitoring, GEM was also evaluated in the vial access device and in the access port system to the intravenous therapy bag of TexiumTM/SmartSiteTM and Equashield® II devices after the reconstitution and preparation steps of the drug. The next checks highlighted GEM dispersion after compounding using TexiumTM/SmartSiteTM, with positive samples ranging from 9 to 23%. In contrast, gemcitabine was not present at detectable levels in the Equashield® II system in all of the evaluated samples. The Equashield® II closed system seems effectively able to eliminate spills and leakage during gemcitabine compounding. Since drugs with different viscosities can have different effects on CSTDs, Equashield® II needs to be considered with other antineoplastic drugs during a structured surveillance program.