Introduction: Second-line antiretroviral therapy (ART) regimens are used when patients develop treatment failure from first-line drug regimens. The present study is aimed to compare treatment outcome in terms of clinical, virological, and immunological effectiveness over 1 year of follow-up in human immunodeficiency virus (HIV) patients, switched to various second-line ART regimens and to assess adverse drug reactions (ADRs). Materials and Methods: A longitudinal observational study was conducted at ART center, SMS Hospital, Jaipur, after approval from Institutional Research Review Board. One hundred HIV positive patients, resistant to first line ART, switched to either of the 2 s line ART regimens were followed for 1 year for early treatment outcomes and any ADRs. Results: Out of 97 patients enrolled 65 patients received Tenofovir and 32 patients received Zidovudine (ZDV) along with lamivudine and Atazanavir/ritonavir. There was significant increment in CD4 count from the baseline value (202.51–438.52 cells/mm3) after 12 months of therapy. On comparison, CD4 cell rise was not significantly different between the two groups. However, Plasma viral load suppression was achieved insignificantly more number of patients in ZDV group than in tenofovir group: 31 (96.9%) versus 57 (87.7%), respectively. Opportunistic infections (OI) were seen in 21.5% and 28.1% patients respectively at the time of switching of second-line ART. Out of 59 ADRs reported, nausea, vomiting, diarrhea, hyperbilirubinemia, dyslipidemia, and anemia were most common. Conclusion: Nonadherence, drug resistance, and treatment failure are the major challenges in controlling HIV disease. Our study shows that both the second-line regimens were comparable in improvement in CD4 count and viral load suppression with 1 year success rate of 90.7%.