The affinity that Violet-green Swallows (Tachycineta thalassina) and especially Tree Swallows (Tachycineta bicolor) have for nest boxes is well known. Nest boxes, properly placed and maintained, may be used for many years. In this note I report the use of plexiglass in the construction of swallow nest boxes. Plexiglass facilitates observation of nesting activities such as incubation, brooding and feeding of young. Prey items may be identified and interactions among young and adults observed. Photographs inside the nest box may also be obtained. Finally, transparent nest boxes can contribute immensely to natural history education of children and adults by providing close observation opportunities without disturbing the birds.