Access to the Barrett Lake is via Porto Rico Road, 15 km south of Nelson off Highway 6. In summer you can drive up 3 km and park there. (Recommended Quad Access Only from this point). From here you take the lower fork in the road up another 3 km (this section of road is deactivated but is passable in a high clearance 4X4) to a junction, take a right here (about 6 KM up in total). From here, follow the really rough and rocky road for another 4.5 Km up to the lake, stay on the main road on the way up. The last 4.5 Km is extremely rough, and heads to the East up the drainage crossing a South facing rocky slope.