The present invention relates to an injection needle assembly having opposite distal and proximal ends, and wherein the assembly comprises an injection needle (46) having proximal (48) and distal (50) pointed ends, wherein the distal pointed end is arranged to penetrate a membrane arranged at the proximal end of a medicament container; a tubular needle holder (40) comprising distal engagement means (44; 70) and proximal engagement means (54); a tubular cap (26) comprising proximal outer engagement means (60; 80) and proximal inner engagement means (36, 38; 72); a tubular needle cover (12) comprising first engagement means (52) arranged to cooperate with the proximal engagement means (54), and second engagement means (58; 78) arranged to cooperate with the proximal outer engagement means (60; 80) of the cap; characterized in that said needle cover is arranged to be displaced from a first position wherein the second engagement means (58; 78) and the proximal outer engagement means (60; 80) prevents the needle cover and the needle holder to be axially displaced by a linear displacement, to a second position wherein the needle cover and the needle holder are distally displaced, and wherein the proximal inner engagement means (36, 38; 72) of the cap and the distal engagement means (44; 70) of the needle holder prevents the needle holder to be proximally displaced but allows the needle cover to be distally displaced.