A rear support assembly of neck collar is provided, including: a nape base, including a main body and two positioning mechanisms, each positioning mechanisms includes at least one stopper, a positioning member and an inserting space, the positioning member having a first combination portion； two support sheets, respectively movably inserted into the inserting space of one of the two positioning mechanisms, the two support sheets each including a plurality of second combination portions, each second combination portions being engageable with the first combination portion of one of the two positioning mechanisms； one of a first guide track and a first rib disposed on the main body, the other of a first guide track and a first rib disposed on one of the two support sheets； one of a second guide track and a second rib disposed on the main body, the other of a second guide track and a second rib disposed on the other of the two support sheets.本發明關於一種頸圈後支撐結構，包括： 一後頸座，包括一本體、二定位機構，各該定位機構包括至少一擋件、一定位件及一插設空間，該定位件設有一第一結合部；二支撐片，分別可移動地插設於其中一該定位機構之插設空間，分別包含有複數第二結合部，各該支撐片之各該第二結合部可選擇性地與其中一該定位機構之第一結合部相互卡抵結合；一第一導軌及一第一凸肋其中一者設於該本體、另一者設於其中一該支撐片；一第二導軌及一第二凸肋其中一者設於該本體、另一者設於另一該支撐片。
