AbstractPresent research evaluates the feasibility of producing polyethylene terephthalate glycol (PETG) filaments reinforced with cenosphere (CS), which have great potential to develop syntactic foam composites (SFC) for several applications, that is, from automotive to aerospace. A melt flow extrusion technique was used to reinforce PETG with different weight fractions (i.e., 0, 10, 20, 30, and 40 wt%) cenosphere, and further, the thermal, mechanical, and physical properties of the prepared feedstocks were investigated in detail. Results indicated that Young's modulus, load‐bearing capacity, and ultimate tensile strength of PETG filament with 40 wt% CS were 1652.1 5 MPa, 76.91 1 N, and 31.97 1 MPa, respectively, which is similar to virgin PETG filament. In addition, the porosity of the CS‐reinforced PETG filaments decreased with increasing concentration of the CS in the PETG matrix. Such cenosphere‐filled filaments possess attractive thermo‐mechanical and physical properties to develop high‐quality SFC through additive manufacturing (AM) routine.Highlights PETG/cenosphere based 3D printing filaments were developed. The modulus and strength significantly improved by adding 40% cenosphere. The porosity decreased with increasing cenosphere weight fraction. Addition of cenosphere affected water absorption characteristics of filaments.