Background: The risk of developing cutaneous T-cell lymphoma (CTCL) in patients with psoriatic disease using tumor necrosis factor inhibitors (TNFi) has not been well characterized. This study aims to review the incidence of CTCL in clinical trials of TNFi and TNF inhibitor biosimilars used to treat patients with psoriasis and other psoriatic diseases. Methods: The US National Library of Medicine clinical trials database (clinicaltrials.gov) was queried to identify all phase 3 and 4 clinical trials of the 5 FDA-approved TNFi and TNFi biosimilar biologic therapies. The search was limited to clinical trials involving psoriatic diseases treated with TNFi and biosimilars. Trials involving the following psoriatic diseases were identified and included: psoriasis, psoriatic arthritis, generalized pustular psoriasis, and palmoplantar pustulosis. The incidence of CTCL in these trials was examined and summarized. Fisher’s exact test was performed to determine differences in the rate of CTCL between patients who received biologic therapy and those who received placebo treatments. A p-value less than 0.05 was considered statistically significant. Results: Data from 98 phase 3 and 4 trials of TNFi and TNFi biosimilars were analyzed. No cases of CTCL were reported in 17,906 patients with psoriatic diseases who received TNFi in phase 3 trials. No cases of CTCL were reported in 4,066 patients with psoriatic diseases who received TNFi in phase 4 trials. No cases of CTCL were reported in 1,621 patients with psoriatic diseases who received TNFi biosimilar in phase 3 trials. There were no TNFi biosimilar phase 4 trials. Of the 3,283 patients who received placebo in phase 3 trials and 248 patients who received placebo in phase 4 trials, no cases of CTCL were reported. No difference was found between the incidence of CTCL in patients treated with TNFi and those treated with placebo in both phase 3 and 4 trials using the Fisher’s exact test (p > 0.05). Lastly, no difference was found between the incidence of CTCL in patients treated with TNFi biosimilars and those treated with placebo using the Fisher’s exact test (p > 0.05). Conclusion: Our findings indicate that the use of TNFi and TNFi biosimilars in the treatment of psoriatic diseases is rarely associated with the development of CTCL.