This study numerically investigates the effects of the number of bottom openings and the fin spacing on both the natural convection heat transfer and airflow field of the handheld projector with various orientations. The horizontally-oriented 120 mm × 53 mm × 19 mm handheld projector, which had 11 bottom openings and was installed with either 7 plate fins or 13 rows of square pin, was considered as the primary case. The fin number varied from 6 plates to 13 plates or from 7 pin rows to 16 pin rows, while the bottom openings varied from 11 to 15 in this study with handheld projector held at a specified inclination ranging from −90 • to 90 • . The results showed that the heat transfer coefficient of a specific surface of the plate-fin array installed in the primary handheld projector increased from 6 to 7 W/m 2 ·K as the heating power increased from 2 W to 7 W. The optimal fin spacing in the handheld projector possessing 11 bottom openings was 2.875 mm and 3.375 mm for the plate-fin and pin-fin, respectively, at a heating power of 7 W. Although the velocity magnitude of the airflow between fins increased as the bottom opening increased, it was not able to offset the reduction of the airflow velocity resulting from the fin spacing reduction.