Trichoderma reesei is the most important industrial cellulase-producing filamentous fungus. Although its molecular physiology has been investigated, the signal transduction pathways are not fully understood. In particular, the role of casein kinase II (CKII) is not yet clear. In this work, we carried out functional investigations on a catalytic subunit of CKII, CKII alpha 2. Comparison of the phenotypic features of T. reesei parent and Delta ck2 alpha 2 strains showed significant changes following ck2 alpha 2 disruption. T. reesei Delta ck2 alpha 2 form significantly smaller mycelial pellets in glucose-containing liquid minimum media, have shorter and fewer branch hyphae, produce smaller amounts of chitinases, produce more spores, show more robust growth on glucose-containing agar plates, and consume glucose at a significantly higher rate. Suggestions can be made that CKII alpha 2 governs chitinase expression, and the disruption of ck2 alpha 2 results in lower levels of chitinase production, leading to a weaker cell wall disruption capability, further resulting in weaker hyphal branching, which eventually leads to smaller mycelial pellets in liquid media. Further conclusions can be made that CKII alpha 2 is involved in repression of sporulation and glucose metabolism, which is consistent with the proposal that CKII alpha 2 represses global metabolism. These observations make the deletion of ck2 alpha 2 a potentially beneficial genetic disruption for T. reesei during industrial applications, as smaller mycelial pellets, more spores and more robust glucose metabolism are all desired traits for industrial fermentation. This work reports novel unique functions of a CKII catalytic subunit and is also the first genetic and physiological investigation on CKII in T. reesei.