3D Plastronics is a technology capable of improving the integration of heterogeneous functions in or on polymer packages of electronic devices by implementation of conductive patterns and electronic components. Among 3D Plastronics technologies, In-Mold Electronics (IME) is a fast-growing emerging manufacturing process for mass production of plastronic devices. It is based on the screen printing of a thermoplastic film (printed electronic process), followed by a 3D shaping using thermoforming and finally a step of overmolding by injection of a thermoplastic polymer. Nowadays, IME is mainly based on PolyCarbonate (PC), which is thus a reference material. The paper focuses on Poly(Lactic Acid) (PLA), a biosourced and biodegradable polymer to reduce the environmental impact of IME manufacturing. The thermal and mechanical properties of the PLA materials are investigated to optimize the IME process parameters and to take into account the glass transition temperature Tg around 55–60°C of PLA. Thermal properties of inks are then considered to adapt drying to the polymer substrate, with the results being a good adhesion (category 0 of the ISO 2409 standard) and sufficient electrical resistivity (290 µΩ.cm) of the ink on PLA. Electronic components are connected to the circuit with conductive and structural pastes giving a shear stress of 9.1 N/mm² on PLA. The next steps of the IME process are also studied, thermoforming and injection molding. An electronic circuit is designed as a demonstration vehicle combining the IME process with PLA as the main structural material.