This study was conducted to investigate the production of an efficient chitinase from a marine isolate. Accordingly, a marine fungus was isolated from the soft coral; Heteroxenia fuscescens and identified by molecular 18S rRNA technique as Penicillium chrysogenum. The isolate was chitinase producer (331, 8 U/mL) and the result was confirmed by TLC and HPLC. The enzyme was partially purified and immobilized completely in a modified bentonite. The free and immobilized enzymes recorded a maximum relative activity (100%) at 50 and 55°C, respectively, the activation energy of the immobilized enzyme was 10.60 Kjmol ^-1 with 40% reduction than that of the free enzyme. Thermal and pH stability studies showed that the enzyme maintained its complete activity at (50 and 55) °C for 120 min and at pH 5 and 6.  The deactivation rate constant (K_d), deactivation energy (Ed), half-life (t_1/2) , D, ∆ G, ∆ H, ∆ S  values were calculated for both enzyme forms and insured the success of the immobilization process in enzyme protection. The immobilized enzyme was reused for three cycles without loss in activity. Toxicological studies of chitinase against 3^rd instar larvae of Cx. pipiens L revealed high mortality rates.