This species is similar in its often relatively smaller leaves and inflorescences that become spiciform to Paederia lanata and Paederia farinosa subsp. rosea, both also found in northern Madagascar. Paederia argentea is distinguished in part by its relatively long slender corolla tubes, 25-45 mm long, and its generally short calyx lobes. Puff (1991) described the calyx lobes as 0.7-4 mm long, but on some specimens annotated by him a few of the lobes reach 5 mm long; in particular, the calyx lobes apparently sometimes elongate a bit as the fruits develop. Puff also described the inflorescence axes as glabrous, but those of some specimens annotated by him have dense short pubescence, variously strigillose to pilosulous.

Paederia lanata differs from Paederia argentea in its dense woolly-hirsute pubescence on the inflorescence axes and ovaries; some specimens appear to be intermediate between these, for the discussion of those see the comments under Paederia lanata. Paederia farinosa subsp. rosea is also very similar to Paederia argentea, and these may deserve re-evaluation now with more specimens available. Paederia farinosa subsp. rosea was separated by Puff based only on its longer calyx lobes, 4.5-15 mm long; however the type specimen of Paederia farinosa subsp. rosea has calyx lobes 3-5 mm long, and appears similar in general aspect also as well as geographic distribution to Paederia argentea.