Substituting petroleum-based plastics with biobased alternatives is critical for eco-friendly and sustainable developments. Although poly(ethylene 2,5-furandicarboxylate) (PEF) demonstrates promising potential in packaging applications due to its excellent gas barrier properties, the lack of toughness remains to be addressed, while the conventional toughening approaches often lead to a significant compromise in thermostability. Herein, a copolymerization strategy was exploited by simultaneously integrating ethylene terephthalate (ET) units and poly(tetramethylene glycol) (PTMG) segments into the backbone of PEF. Owing to the rational chain-polarity, chain-flexibility and bonding energy regulation, toughness and thermostability of the resultant copolyesters are well-balanced. When the molar ratio of terephthalic acid/2,5-furandicarboxylic acid is controlled at 3:7, and the mass fraction of PTMG accounted for 30 wt% of ethylene glycol, the elongation at break of PEFT30MG30 is significantly increased from 2.9 % to 138.3 %, accompanied by a remarkable increase in toughness to 38.3 MJ/m3, as well as maintaining a high 5 % weight loss temperature of 363.2 °C. Although the gas barrier properties are inevitably compromised, they still remain comparable states of petroleum-based poly(ethylene terephthalate) packaging materials. This study presents an effective molecular-level strategy to toughen PEF, highlighting a feasible path for practical applications.