This study explored the effect of short and focused mathematical instruction provided in chemistry course on student chemistry achievement in New York City Title I high school. This study followed quasi-experimental nonequivalent control group design and was guided by the following research questions: 1) What is the effect of short mathematics instruction on student chemistry achievement?, and 2) Is there a relationship between mathematics performance of students who had been exposed to short mathematics instruction at the beginning of each chemistry lesson and their chemistry achievements? The pre/post test analysis indicated that students in the experimental group significantly outperformed their peers in the control group. The study found strong positive correlation between student chemistry and mathematics scores.