This paper studies generalized signcryptions in the certificateless public key settings. The paper proposes the formal definition and security model of certificateless generalized signcryption. The Type II adversary in the security model is malicious, but a passive Type II attacker. Also an efficient construction of certificateless generalized signcryption scheme using bilinear maps is also implemented. The security of proposed scheme is based on the infeasibility of the Computational Diffie-Hellman problem and Decision Bilinear Diffie-Hellman problem. The scheme is formally proven without random oracles under the security model of certificateless generalized signcryption schemes. Due to its security, high efficiency and freedom from certificate management, it may have practical applications in electronic cash payment, firewall and key distribution, etc.