An implantable lead assembly (100; 210; 310) comprising: an elongated lead body (71, 301) having a proximal end, being the end of the lead body (71, 301) configured to be connected to a housing of an active implantable medical device, and a distal end, being the opposite end of the lead body (71, 301) configured for sensing and/or stimulating a tissue, and at least one lead lumen; and at least one electrically conductive wire (81, 82, 83; 304a-304d) arranged in said at least one lead lumen; said at least one electrically conductive wire (81, 82, 83; 304a-304d) being in electrical contact, at the distal and proximal ends (73, 72), with a respective distal or proximal electrically conductive member (75, 76, 77, 78, 79, 80; 307a-307d) provided on an outer circumference of the lead body (71; 301); characterized in that the implantable lead assembly (100; 210; 310) further comprises, mounted over the proximal end, an electrical connector cap (20, 60); the electrical connector cap (20, 60) comprising an elongated cap body having at least one cap lumen and at least one through hole (24, 25, 26) extending from an outer surface of the elongated cap body into the cap lumen; and at least one electrically conductive member (28, 29, 30; 50) of the electrical connector cap (20, 60) arranged on an outer circumference of the elongated cap body over said at least one through hole (24, 25, 26) of the elongated cap body; wherein said at least one electrically conductive member (28, 29, 30; 50) of the electrical connector cap (20, 60) comprises at least one through hole (31, 32, 33; 54) extending from an outer surface of the electrically conductive member (28, 29, 30; 50) of the electrical connector cap (20, 60) into the cap lumen through said at least one through hole (24, 25, 26) of the elongated cap body; wherein the electrical connector cap (20, 60) is arranged such that the proximal electrically conductive member (78, 79, 80) provided on the outer circumference of the lead body (71; 301) at least partially contacts a respective electrically conductive member (63, 64, 65) of the electrical connector cap (20, 60); wherein the elongated cap body is a one-piece component made of a biocompatible insulating material. an elongated lead body (71, 301) having a proximal end, being the end of the lead body (71, 301) configured to be connected to a housing of an active implantable medical device, and a distal end, being the opposite end of the lead body (71, 301) configured for sensing and/or stimulating a tissue, and at least one lead lumen; and at least one electrically conductive wire (81, 82, 83; 304a-304d) arranged in said at least one lead lumen; said at least one electrically conductive wire (81, 82, 83; 304a-304d) being in electrical contact, at the distal and proximal ends (73, 72), with a respective distal or proximal electrically conductive member (75, 76, 77, 78, 79, 80; 307a-307d) provided on an outer circumference of the lead body (71; 301); characterized in that the implantable lead assembly (100; 210; 310) further comprises, mounted over the proximal end, an electrical connector cap (20, 60); the electrical connector cap (20, 60) comprising an elongated cap body having at least one cap lumen and at least one through hole (24, 25, 26) extending from an outer surface of the elongated cap body into the cap lumen; and at least one electrically conductive member (28, 29, 30; 50) of the electrical connector cap (20, 60) arranged on an outer circumference of the elongated cap body over said at least one through hole (24, 25, 26) of the elongated cap body; wherein said at least one electrically conductive member (28, 29, 30; 50) of the electrical connector cap (20, 60) comprises at least one through hole (31, 32, 33; 54) extending from an outer surface of the electrically conductive member (28, 29, 30; 50) of the electrical connector cap (20, 60) into the cap lumen through said at least one through hole (24, 25, 26) of the elongated cap body; wherein the electrical connector cap (20, 60) is arranged such that the proximal electrically conductive member (78, 79, 80) provided on the outer circumference of the lead body (71; 301) at least partially contacts a respective electrically conductive member (63, 64, 65) of the electrical connector cap (20, 60); wherein the elongated cap body is a one-piece component made of a biocompatible insulating material.