<P><B>Abstract</B></P><P>Photobiological hydrogen production plays a vital role in generating clean renewable energy owing to its low energy consumption and environmental friendliness. Although materials‐induced <I>Chlorella</I> aggregates have been developed to achieve sustained photobiological hydrogen production under normal aerobic conditions, the yield is relatively low and equals only 0.42 % of the light‐to‐H<SUB>2</SUB> energy‐conversion efficiency. Herein, we report that only 0.5 vol % dimethyl sulfoxide in an aqueous environment significantly enhances the H<SUB>2</SUB> yield produced by aggregated <I>Chlorella</I>, reaching 0.69 % of the light‐to‐H<SUB>2</SUB> energy‐conversion efficiency. This improvement can be attributed to an increase in the cellular respiration rate by dimethyl sulfoxide, which results in a decrease in the oxygen content inside the aggregates and, ultimately, to the activation of more hydrogenases. More generally, this strategy consists of a functional enhancement in organism–material hybrids by using small molecules.</P>