[1] Pseudoanthidium tenellum is found from North Africa to Algeria.

In Eurasia from eastern Germany and Austria eastwards to Bulgaria, according to an isolated report from Tajikistan (Popov 1967).

The species was first recorded in Germany in 1996 in Saxony-Anhalt, followed by further finds there in 2001 and 2002 (Burger & Ruhnke 2004).

[1] The species nests inside galls formed by Lipara flies.

P. tenellum feeds on pollen sources, mainly from wetland plants in Bidens and Pulicaria genera.