This study was conducted to evaluate the effect of dietary ${eta}$-mannanase supplementation and palm kernel meal (PKM) inclusion (5%) on laying performance, egg quality and nutrient utilizability of laying hens with 73 weeks of age. A total of 240 Lohmann brown laying hens with average 77.5% egg production were randomly allocated with 60 hens per treatment, 4 replicates per treatment and 15 hens per replicate. Experimental design was a completely randomized design with $2{ imes}2$ factorial arrangement, with the factors being (1) two levels of PKM (0 vs. 5%) and (2) with or without dietary ${eta}$-mannanase (480 IU/kg of diet CTCzyme$^{(R)}$) supplementation. All hens were housed in cages ($35cmW{ imes}35cmD{ imes}40cmH$) with 2 hens per cage for six weeks feeding trial. Laying performance was recorded daily during feeding trial. Egg quality, nutrients utilizability and blood assays were done at the end of feeding trial. Egg production was improved (P<0.05) by both dietary PKM inclusion and ${eta}$-mannanase combined supplementation. Either ${eta}$-mannanase or PKM did not affect feed intakes and feed conversion ratio of all diets. Egg weight of hens fed diet containing 5% of PKM had heavier (P<0.05) eggs compared with hens fed without PKM. Albumen height was improved (P<0.05) by dietary mannanase supplementation. Crude fat utilization of 5% PKM diet was higher than that of no PKM diet regardless of ${eta}$-mannanase supplementation. Both DM and total carbohydrate utilization were decreased (P<0.05) in hens fed 5% PKM diet. Serum IgG and yolk IgY contents of PKM groups were lower (P<0.05) than those of no PKM groups. This result showed that 5% PKM diet, independent of dietary ${eta}$-mannanase supplementation, was able to improve egg production. In addition, dietary ${eta}$-mannanase supplementation could be used for improving the albumen height of eggs.