If driving, proceed mauka on Tantalus Drive. When you get close to the top, look for the trailhead sign behind the guardrail on the right side of the road. There is trail parking in the small lot just before the trailhead on the left side of the road.
Please note that Nahuina Trail (in yellow) is part of the Honolulu-Mauka Trail Network, comprising of 18 interconnected trails (in turquoise). The system may be accessed via the Makiki Arboretum Trail (dark blue) as part of an extended hike. The shortest route from the Makiki Arboretum Trail to the Nahuina trailhead is 1.4 miles.
The Nahuina Trail starts at a signed junction by the guardrail along Tantalus Dr. Descend gradually on four long switchbacks. Contour along the side of a ridge, crossing several gullies. Reach the end of the Nahuina Trail at a signed junction with the Makiki Valley Trail.