91.5% of the total population are Germans (49.3% male and 50.7% female) and 8.5% are "not Germans" (52.4% male and 47.6% female)[3] Population of each village (as of 30 June 2022)[4] (last municipal election: 14 March 2021)[5] Lahntal's civic coat of arms might be described thus: In gules an inescutcheon showing the shield of the Teutonic Knights (in argent a cross sable), laid over a fess wavy argent; behind the inescutcheon tilted dexter and turned sinister an abbess's staff Or with velum argent; spangled with seven trefoils, three above the fess and four below.

The coat of arms was adopted as part of the municipal reform in Hesse, and the wavy fess represents the community's namesake river.

Lahntal has been partnered since 6 April 1986 with the community of Sussargues, which lies in the department of Hérault in southern France, right near Montpellier (about 17 km) and the Mediterranean Sea.

Running west–east through the municipal area is the Federal Highway (Bundesstraße) B 62 coming from Biedenkopf and going on towards Cölbe and farther to Alsfeld.

The Obere Lahntalbahn, a single-track Deutsche Bahn unelectrified secondary railway line run by DB's Kurhessenbahn subsidiary, joins Marburg by way of Biedenkopf and Bad Laasphe with Erndtebrück.