About 83% of lending to the Kenyan mortgage market was carried out by only 8 out of the 39 registered banks as at December 2022. This study sought to establish the influence on focus strategy on Mortgage Performance of banking institutions in Kenya. The study was based on the theories of Porter’s Generic Strategies and Resource-Based View (RBV) of competitive advantage. To achieve the research objective, a sample of 30 commercial banks was studied out of the entire accessible population of 39 banks in the cities of Nairobi, Mombasa, Nakuru, and Kisumu. Questionnaires, with 5-point Likert-scale responses, were administered to the respondents. There were five respondents drawn from the mortgage experts in each bank making a total of 150 respondents with a response rate of 78.7%, that is, 118 achieved. The data gathered was presented using descriptive statistics with mean, for measuring central tendency while standard deviation measured dispersion of the responses, as well as frequencies. Regression results showed that focus strategy explained 28.2% of variation in mortgage performance and had statistically significant and strong positive influence on mortgage performance. Bank size, however, did not have a statistically significant moderating effect on the relationship between focus strategy and mortgage performance, as justified by the interaction term’s p-value of 0.367 that was greater than 0.05. Consequently, the study failed to reject the second null hypotheses. Banks, in the small and medium peer groups, should adopt more focus strategies as opposed to mass-market strategies that are more suited for larger banks.