To create an HIV-1 vaccine that generates sufficient breadth of immune recognition to protect against the genetically diverse forms of the circulating virus, we have been exploring vaccines based on consensus and mosaic protein designs. Increasing the valency of a mosaic immunogen cocktail increases epitope coverage but with diminishing returns, as increasingly rare epitopes are incorporated into the mosaic proteins. In this study we compared the immunogenicity of 2-valent and 3-valent HIV-1 envelope mosaic immunogens in rhesus monkeys. Immunizations with the 3-valent mosaic immunogens resulted in a modest increase in the breadth of vaccine-elicited T lymphocyte responses compared to the 2-valent mosaic immunogens. However, the 3-valent mosaic immunogens elicited significantly higher neutralizing responses to Tier 1 viruses than the 2-valent mosaic immunogens. These findings underscore the potential utility of polyvalent mosaic immunogens for eliciting both cellular and humoral immune responses to HIV-1.