The aim of the investigations was the manufacturing and characterisation of fully biobased polymer composites with good mechanical performance and advantageous morphology‒property relationships. As matrix material, the biobased semi-crystalline polymer polybutylene succinate (PBS) was used, a linear aliphatic polyester exhibiting a higher biodegradability compared to PLA, even in fresh and seawater. However, with methods to characterize the morphology of isothermally crystallized PBS it has been shown that the spherulitic morphology of PBS highly varies from rather fine-spherulitic to highly coarse-spherulitic within a relatively small temperature range. One way to trigger the mechanical performance including the toughness even at low temperatures is to modify PBS with natural rubber latices using a solution process with additional direct injection moulding. Furthermore, it has to be highlighted that PBS (similarly to PP) can be nucleated (for instance by cellulose (nano)fibres), which is a basic requirement to adjust the semi-crystalline morphology. Therefore, the impact of natural short-fibres on the crystallization behaviour and the mechanical performance was analysed. The results of the mechanical investigations showed that both the modulus of elasticity and hardness are highly increased, particularly for the argeli-fibre composites without any agglomeration of the fibres.