The present study reports the results of a field and laboratory based experiment conducted to assess the effects of different pH ranges of simulated acid rain (2.5, 3.5, 4.5, 5.5 ) on chlorophyll and ascorbic acid contents in two cultivars (cv.IC-75730 and cv.Local ) of a medicinal herb Ocimum sanctum. Chlorophyll and ascorbic acid contents of leaves were adversely affected at pH 2.5 and 3.5. The effects of simulated acid rain became more pronounced with the increase in acidity of rain and the duration of treatments. Chlorophyll-a showed more reduction than chlorophyll-b. In both the cultivars cv. Local was found more sensitive than cv.IC-75730 for chlorophyll and ascorbic acid rain contents. For the study showed that acid rain has in a negative impact on Ocimum sanctum plant performance.