An investigation of the growth response of fluted pumpkin to different combinations of irrigation intervals and spent mushroom substrate (SMS) was conducted during the dry season, with a view to determining the combination that would give the best performance of the crop. The experiment lasted for a period of thirteen weeks in a sandy loam soil. Three irrigation intervals of 4, 7 and 10 days, and three levels of SMS, 10, 20 and 30 t/ha were randomly combined, including a control with neither irrigation nor SMS. Results indicate that there were significant differences in growth parameters such as vine length, number of leaves, leaf area, number of branches, vine fresh weight and total shoot yield across the treatment variants. The combination of 7 days irrigation interval and 20 t/ha SMS gave the highest mean vine length of 1.99 cm, while the greatest mean leaf area (75.95 cm 2) was obtained from the combination of 4 days irrigation interval and 20 t/ha SMS. However, the combination of 4 days irrigation interval and 30 t/ha SMS gave the highest mean number of leaves (54), number of branches (9.67), vine fresh weight (2.15 t/ha), percent emergence (92.88%), and total shoot yield (2.17 t/ha). The results of this study therefore suggested that the best growth performance of fluted pumpkin during the dry season is obtainable from a combination of 4 days irrigation interval and 30 t/ha SMS.