In this study, the effects of the stroke/bore (S/B) ratio on the performance parameters of an engine having dual-spark ignition (DSI) were investigated theoretically by using a quasi-dimensional thermodynamic cycle model. A range of S/B ratios for various spark-plug locations were examined in the scope of the study. The engine performance parameters, i.e., engine power, indicated mean effective pressure, specific fuel consumption, and thermal efficiency, were computed for various conditions. The obtained results for DSI operation have been compared to those of a single-spark-ignition (SSI) condition. Such comparisons showed that increases in the S/B ratio cause improvements in engine performance parameters. The dual-plug operation also improves the overall engine performance at different percentages for the selected S/B ratios.