<jats:p>Some corn genotypes produce husk leaves, i.e., laminae extending from the husk. However, the role of husk leaves in grain production is unclear. Hydroponic and field experiments were conducted to determine the contribution of husk leaves to dry matter and grain production and the characteristics of photosynthesis and translocation of <jats:sup>13</jats:sup>C‐labelled photosynthate of the husk leaves in comparison to culm leaves. A husk leaf and calm leaves at different positions of hydroponically grown sweet corn (<jats:italic>Zea mays</jats:italic> L. cv. Laramie 83) were exposed to <jats:sup>13</jats:sup>CO<jats:sub>2</jats:sub>. Field treatments consisted of a control and partial or complete defoliation at the silking stage. The <jats:sup>13</jats:sup>CO<jats:sub>2</jats:sub> feeding in both experiments and measurement of field photosynthetic rate were made 14 d after silking. Husk leaves alone produced ≈45% of the whole plant weight and grain yield, respectively, relative to the control plants. Dry matter and grain production per unit leaf area was greater for the husk leaves than culm leaves of defoliation plants. Photosynthetic rate of the husk leaves was almost equivalent to that of culm leaves of the control plants. Percentage export of <jats:sup>13</jats:sup>C from husk leaves (96–97%) was higher than from culm leaves (87–92%). Percentage of plant <jats:sup>13</jats:sup>C was highest in the ear (45–87%), followed by the culm. When <jats:sup>13</jats:sup>CO<jats:sub>2</jats:sub> was fed to a husk leaf, defoliation increased <jats:sup>13</jats:sup>C accumulation in the ear but decreased it in other parts. When <jats:sup>13</jats:sup>CO<jats:sub>2</jats:sub> was fed from a culm leaf, however, the reverse trend was true. These results suggest that the husk leaves play an important role in grain production due to efficient translocation of photosynthate.</jats:p>