The sailing safety constraints of containerships were ignored in the previous studies on feeder containership routing problems; however, they are especially critical for small-sized feeder containerships. In this study, we optimize feeder routes while incorporating stowage plans to address the sailing safety of containerships. Firstly, a mixed integer nonlinear programming model for integrated optimization is formulated. Next, a heuristic algorithm is designed, by which feeder routes can be updated through a variable neighborhood search, and stowage plans are obtained using a genetic algorithm. Finally, through the computational study, we confirm that the integrated optimization can meet the sailing safety requirements of containerships and effectively reduce the total cost of the feeder service. Moreover, through the sensitivity analysis, we discuss the performance robustness of the proposed algorithm and further demonstrate the significance of this study. [ABSTRACT FROM AUTHOR]