Prompt entry to care after HIV diagnosis benefits the infected individual and reduces the likelihood of further transmission of the virus. The New York State HIV Testing Law of 2010 requires diagnosing providers to refer persons newly diagnosed with HIV to follow-up medical care. This study used routinely collected HIV-related laboratory data from the New York State HIV surveillance system to assess whether the fraction of newly diagnosed cases entering care within 90 days of diagnosis increased after the implementation of the law. Laboratory data on 23,302 newly diagnosed cases showed that entry to care within 90 days rose steadily from 72.0% in 2007 to 85.4% in 2012. The rise was observed across all race/ethnic groups, ages, transmission risk groups, sexes, and regions of residence. Logistic regression analyses of entry to care pre-law and post-law, controlling for demographic characteristics, transmission risk, and geographic area, indicate that percentage of newly diagnosed cases entering care within 90 days grew more rapidly in the post-law period. This is consistent with a positive effect of the law on entry to care.