Bulk lipid transport between organelles has been proposed to involve the partnership between bridge-like lipid transfer proteins (BLTPs) and membrane-embedded lipid scramblases. However, for almost all BLTPs, such physical association has not been fully described and, in most cases, the identity of the scramblases is unknown. Here we identify TMEM170-family proteins as endoplasmic reticulum lipid scramblases that physically interact with BLTP1/Csf1 proteins and we provide a revised model detailing the structure of this protein complex in Caenorhabditis elegans. This finding opens avenues to understand the mechanistic basis of lipid transport at membrane contact sites.