With the increasing environmental pollution and strict requirements for energy conservation and emission reduction, multi-material lightweight structures consisting of Al alloys and plastics are leading the direction of lightweight design in automobile industry. In this study, a laser beam with varied laser powers was used to construct grooves and textures on 5182 aluminum alloy (5182Al) to obtain tight joints with polyether ether ketone (PEEK) through hot-pressing joining. Systematic investigations including surface microscopic analysis, mechanical tensile shear tests, and chemical bond analysis were performed to reveal the underlying bonding mechanisms and debonding mechanisms of 5182Al/PEEK hot-pressing joints. The results showed that the tensile shear strength of the 5182Al/PEEK hot-pressing joints reached a maximum value of over 20 MPa, which indicated the high strength and reliability of joints. Moreover, intensive investigations revealed that the bonding mechanisms of 5182Al/PEEK hot-pressing joints after laser surface treatment were determined to be mechanical interlock and chemical connection, and a higher laser power was conductive to improving these two effects thus facilitating the bonding strength. This study provided a practical approach and theoretical reference for improving the bonding strength of 5182Al/PEEK hot-pressing joints for lightweight application in automobile industry.