A needle assembly (10) with safety system (14) comprising: a connector (12)； a needle (14) attached to said connector (12), said needle (14) having a distal end (30), formed for insertion into a patient, and a proximal end (32)； a protector (16) having a tubular body with a proximal end (34) and a distal end (36), an opening (38) being formed in said distal end (36) to allow passage thereof through said distal end (30) of said needle (14) said protector (16) being axially movable relative to said connector (12) from a first position to a second position, said needle (14) extending through said opening (38) and said distal end (30) of said needle (14) being exposed with said protector (16) in said second position； and, a movable locking tongue (18), said locking tongue (18) having a first position that sufficiently covers said opening (38) to prevent the passage thereof through said distal end (30) of said needle ( 14)； and, a solicitation element (20) for pushing said locking tab (18) to said first position； wherein said locking tab (18) is detachably retained in a retained position before the use of the needle assembly (10) with safety system, said opening (38) being sufficiently uncovered with said locking tongue (18) being in said retained position to allow said distal end (30) of said needle (14) through said opening (38), said locking tab (18) being held in said retained position against the pushing force of said element of solicitation (20)； and, wherein, said guard (16) being displaced from said first position to said second position, said locking tab (18) is released from said retained position and is pushed towards said first position under the force of said solicitation element (20), characterized in that said locking tab (18) does not strike or is applied to said needle (14) during an injection or before the complete protection of said needle (14).Un conjunto (10) de aguja con sistema de seguridad (14) que comprende: un conector (12)； una aguja (14) fijad
