This article presents a class of simultaneous transmitting and reflecting pattern manipulation structures (STAR PMS) using 3-D transmission-line-based elements. First of all, the 3-D element is realized by compositing slotlines and microstrip lines together, which obtains a transmitting channel and a reflecting channel. To analyze the operating principle of the proposed element, an equivalent transmission line (TL) model is established, corresponding to the receiving structure and transmitting (or reflecting) structure in each channel. In this way, the transmission and reflection characteristics of our element can be designed with good independence, accuracy, and flexibility through the use of the synthesis method. Then, such elements are quasi-periodically arranged in a transverse plane, where the transmission and reflection phases of each element are adjusted according to the desired performance by virtue of the true-timedelay line. As such, the pattern of transmitted and reflected waves can be simultaneously manipulated. To verify our proposed design concept, a prototype is finally implemented from element synthetic design and simulation to array fabrication and testing. Measured results show a transmitting angle of (θ_t = 150° and ϕ_t = 90°) and a reflecting angle of (θ_r = 30° and ϕ_r = 90°) within the operating bandwidth of 74.3% (from 5.5 to 12 GHz), where the highest efficiencies for transmitting and reflecting manipulation are 32.2% and 36.7%, respectively. Therefore, the proposed STAR PMS can be viewed as one of the potential candidates for achieving full space electromagnetic (EM) environment reshaping in future wireless networks.