Selenium sulfide (SeS2) encapsulated into 3D interconnected mesoporous carbon aerogels (MCA) as a selenium sulfide/carbon composite material was prepared for lithium batteries. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations show the mesoporous structures of the carbon aerogels and the homogeneous distribution of selenium sulfide in the composite. The electrochemical performances of the selenium sulfide@mesoporous carbon aerogel (SeS2@MCA) composite cathode was evaluated using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. It is found that the SeS2@MCA cathode shows a better electrochemical performance than the pristine SeS2 cathode. The SeS2@MCA composite with selenium sulfide content of 49.3 wt.% displays an initial discharge capacity of 1150 mAh g−1 at 50 mA g−1 and a reversible discharge capacity of 601 mAh g−1 after 10 cycles at 500 mA g−1. The better electrochemical performance benefit from the high electron conductivity and 3D interconnected porous structures of the carbon aerogels, which contribute to dispersing SeS2 and trapping polysulfide and polyselenide intermediates within the skeleton structure of the mesoporous carbon aerogels.