Liquid to air membrane energy exchanger (LAMEE) is the most important component in a liquid desiccant air conditioning system. Three main configurations of LAMEE are presented in the literature: co-current, counterflow, and cross-counter flow. In this paper, we evaluated the performance of a counterflow LAMEE dehumidifier in terms of its cooling capacity (CC) and moisture removal rate (MRR). A numerical model was developed and validated with experimental results. The impact of solution properties and inlet air characteristics on the LAMEE’s performance were investigated. Simulation results show that CC and MRR are enhanced by decreasing the temperature and increasing the concentration of the liquid desiccant simultaneously. In order to obtain an optimal performance of the LAMEE, the solution mass flow rate should be equal to or slightly higher than the inlet air mass flow rate. On the other hand, we found that both CC and MRR increase with increasing inlet air temperature and relative humidity. Even though solution properties and inlet air characteristics affect the MRR and the CC, they have a negligible effect on the required air sensible cooling to meet the supply air condition (Qsen). The characteristics of outlet air provided by the LAMEE are in a stable state condition, which proves that the LAMEE has a wide range of adaptability in different operating conditions.