In pediatric clinic practice, bulk fill composite is gaining importance for shortened clinical time with a limited shrinkage. The present study evaluated the 1 year clinical performance of bulk fill composite and conventional composite material in occlusal caries of primary molars. The study was designed as randomized single blind clinical trial and a total of 160 restorations were placed in the cavities of the 80 patients. Each patient received two restorations: one with Filtek Z250 (3M ESPE, St Paul, MN 55144, USA); the other restored with Filtek Bulk-Fill Restorative (FBF) (3M ESPE, St Paul, MN, USA). All restorations were clinically evaluated after baseline, 6 months, and 1 year in terms of retention, color matching, marginal discoloration, marginal adaptation, secondary caries, surface texture, anatomic form, and postoperative sensitivity. Besides the descriptive statistical methods, the Friedman test and the Wilcoxon Signed Ranks were used. Bulk fill was found to be worse compared to control with regard to postoperative sensitivity at baseline without statistical significance (P > 0.05). All of the evaluated restorations were retained and were still in function after 1 year (P > 0.05). With respect to marginal discoloration and marginal integrity, there were no significant differences between bulk fill and composite restorations at all intervals (P > 0.05). Based on this short term data, restoration of Class I cavities with both bulk fill and conventional composite restorations can be performed successfully. Postoperative sensitivity can be an issue with the restorations completed with Bulk fill restorative.