These datasets comprise data obtained during a 42 week-long exposure experiment of Mytilus spp. to two types of microplastics, namely spherical polystyrene (PS) particles and irregular polyvinylchloride (PVC) particles. This data was obtained from January 2018 to January 2019 from juvenile blue mussels with an initial size of 10mm. We recorded growth via shell length, body condition index, byssus thread production in 24 hours and clearance rate of the food algae R. baltica. Growth was measured every six weeks already during a three months acclimation period without exposure to microplastics, while byssus thread production and clearance rate were measured every six weeks only during microplastic exposure. Body condition index was measured two times, at week 16 and 32, while oxidative stress in the form of Malondialdehyde (MDA) concentrations and Superoxide (SOD) activity was only measured once at the end of the experiment. Mussels were exposed to three concentrations of PS (15, 1500, 15 000 particles/individual/week) and five concentrations of PVC (15, 1500, 15 000, 150 000 and 1 500 000 particles/individual/week) and one group to no particles at all as control.