Background The use of biological therapy has been linked with an increased risk of tuberculosis (TB) reactivation. Objective The aim of this study was to present the follow-up results for Isoniazid (INH) chemoprophylaxis in patients with psoriasis receiving different biological therapies. Methods In this prospective observational study, patients with latent tuberculosis infection (LTBI) were given INH chemoprophylaxis between two and nine months prior to the beginning of biological therapy. All patients were followed up monthly for any signs or symptoms of active TB or INH toxicity. Results A total of 101 patients, 44.5% females, with a mean age of 46.9 ± 11.5 years (20–73) were enrolled. LTBI was identified in 100 patients (99%), of whom 81.2% completed nine months of chemoprophylaxis. Three patients (2.9%) developed active TB and 17 patients (16.8%) developed intolerance or toxicity related to INH. Conclusions Chemoprophylaxis with INH seems to be effective and safe for the prevention of most TB reactivations in individuals with LTBI receiving biological therapy, but toxicity must be monitored during follow-up.