Background:HIV is a global pandemic with a prevalence of 0.3% as in 2015 according to NACO. Materials & Methods:Blood sample of 300 HIV positive patients on HAART was collected from ART centre, KIMS, Bangalore. CD4 count, complete hemogram and peripheral smear was studied in comparison to their HAART naïve status over a period of 18 months. Results: A total of 300 HIV positive patients were evaluated, pre and post HAART in which anaemia was the most common haematological abnormality. Leucopenia, lymphopenia, neutropenia & thrombocytopenia were other abnormalities observed, all of which correlated with CD4 count & disease progression. Post HAART, there is significant improvement in all these abnormalities proving the efficacy of HAART. Conclusion: Haematological abnormalities such as anaemia, leucopenia, leucocytosis, neutropenia, neutrophilia, lymphopenia, lymphocytosis and thrombocytopenia are common in HIV infected individuals.Anaemia is the most common haematological abnormality and most frequent type is normocytic normochromic anaemia. Post HAART macrocytosis is common in occurrence due to the effect of zidovudine.HAART is an effective therapy as it improves haematological parameters and haematological parameters can be used as an alternative to CD4 count in resource poor settings.