A series of novel random copolymers of poly(butylene succinate-co-ethylene terephthalate) were synthesized and characterized in terms of thermal and mechanical properties, crystallinity and biodegradability. The composition and microstructure of the prepared copolyesters were characterized by 1H NMR and 13C NMR, respectively. It was seen that the PBS sequence length decreases with ethylene terephthalate content. All copolymers are semi-crystalline and crystallinity and crystallite size decrease slightly with the comonomer content up to 10%, but the introduction of 20% comonomer leads to decrease the crystallinity up to 29%. The melting temperature of copolyesters decreases with the comonomer content according to the Baur’s equation that indicates only PBS blocks crystallize and crystallite size is decreased with the comonomer content. It was also investigated that the elastic modulus also decreases slightly with the comonomer content. However, the elongation at break increases by 500% due to the decrease in crystallite size and crystallinity. Incorporating non-biodegradable aromatic comonomer has a little effect on copolyester degradability because of the randomness and lower crystallite size.