This paper investigates the spectrum estimation (SE) in cognitive radio (CR) using the non-parametric multitaper method (MTM) and higher-order space-time block-code (STBC). Conventional SE methods usually suffer problems from biasing and leakage dilemma and the MTM is considered as an enhancement against such challenging situations. The STBC techniques help alleviate the multipath fading effects in wireless channels and hence improve the overall wireless link performance. The integration of MTM and STBC for SE will be developed using quadrature approximation and assessed using analytical and simulation methods. The simulation results revealed favorable MTM performance gains compared to other classical methods like Periodogram and also the STBC over MIMO for the same test settings.