This study evaluates the feasibility of incorporating reject fibres from paper recycling into wet process fibreboards as a partial replacement for virgin wood fibres. The rejects were obtained from newspaper and magazine paper recycling in the form of sludges. Three sludges were obtained from the process steps: coarse screening, fine screening, and flotation. Fibre size and inorganic contents of these fibres are presented. Incorporating rejects into a single layer panel has a negative impact on the visual appearance of the panels. Therefore, a method of making multi-layer fibreboards which permits the inclusion of rejects in the core layer was developed. The board performances were assessed according to EN 310, EN 317 and EN 319. The results indicate that the quantity of rejects incorporated into the panels must be limited. The maximum amount of the rejects, which do not significantly affect board performance, is estimated to be 10 %.