Calvert Street Investment Partners | 2,157 followers on LinkedIn. Founded on the principles of integrity, accountability and collaboration, Calvert Street Investment Partners has been building and growing companies in the lower middle market for three decades. The firm has consistently evolved yet remains focused on driving family, founder and owner-operated businesses to their potential and generating exceptional results for its investors. Our deep business acumen and experience throughout a company’s capital structure, allows us to continually seek value opportunities for our portfolio companies and our investors.