Direction of dentin tubules is an important factor that affects bond strength of contemporary adhesive materials. Because conservative proximal cavity preparations in primary teeth contain more dentin tubules running oblique or parallel to the cavity walls, this study was conducted to evaluate the influence of tubule orientation on the bond strength to primary dentin. A polyacid-modified resin composite material was used as the test material. A microtensile test was utilized to enable evaluation of bond strengths in three different tubule orientations (perpendicular, oblique, parallel) following aging of the resindentin bonds by long-term immersion of the test samples in water. Samples bonded parallel to the dentin tubules showed the highest microtensile bond strength, followed by the oblique and perpendicular groups. Statistical analysis of the data showed no significant difference between the bond strength of parallel and oblique groups. Independent of the tubule orientation, all samples revealed cohesive fracture within dentin.