3D printing is a popular technique for fabricating three-dimensional solid objects from a digital design. In order to produce high quality 3D printed parts, the appropriate selection of printing parameters is crucial. This research is focused on studying the properties of 3D printed specimens (i.e., mechanical, thermal and morphological) with varying processing conditions such as infill pattern, infill density and infill speed, and also with different printing materials. A number of testing techniques such as tensile, bending, compression, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), thermal imaging, and scanning electron microscopy (SEM) were used for performing a comprehensive analysis. The results showed that Young's modulus of the printed parts increased with the increase of infill density. For pure PLA, parts with 100% infill density obtained the highest Young's modulus of 1538.05 MPa. Of the tested infill speeds from 70 to 110 mm/s; 90 mm/s infill speed gave the highest Young's modulus for pure PLA. Meanwhile, there was a slight difference of Young's modulus between low speeds (70 mm/s and 80 mm/s) and high speeds (100 mm/s and 110 mm/s) compared to the commonly used infill speed of 90 mm/s. The level of crystallinity of the 3D printed PLA specimens did not directly influence the mechanical properties as was confirmed by the DSC results. SEM images showed that the strength of the printed samples was dependent upon the arrangement of their layers. Furthermore, it was found that the most appropriate processing temperature and infill speed for pure PLA filament are 215 °C and 90 mm/s, respectively. Among the five printing materials tested, carbon fibre reinforced PLA (CFR-PLA) gave the highest Young's modulus of 2637.29 MPa at 90 mm/s. Voids inside the matrix and the gaps between layers lead to initiation of cracks of the specimens. Overall, 100% infill density, 90 mm/s infill speed, 215 °C of set nozzle temperature, and the linear fill pattern were the possible optimal process ...