This study aims to produce the poly(lactic acid) (PLA)/teak wood composite filament for 3D printing application. Prior to the production of the wood plastic composite (WPC) filaments, PLA was modified to remedy the problem of brittleness and low-melt viscosity by core-shell rubber (CSR) particles and acrylic processing aid (APA). Two different particle sizes of teak wood flour (WF) were added to the modified-PLA (mPLA). Silane coupling agent was further added to improve the interfacial adhesion between the hydrophilic WF and hydrophobic mPLA matrix. Experimental results indicated that all formulations could be fabricated as 3D printing filaments. However, the filaments were successfully printed only for the mPLA with 74 μm WF. For 125 μm, the printer nozzle was clogged up with the agglomerated WF. WPC filaments had higher water uptake than those mPLA and neat PLA, but it significantly decreased with the silane compatibilisation. SEM result also confirmed the improvement of the interfacial bonding between mPLA and WF, which facilitated better fibre-matrix stress transfer and improved the overall mechanical strength.