Pembrokeshire is thought to be the first 14-19 learning network in Wales not to offer German as an ASA2 option after the last two secondary schools teaching the subject announced that this year's cohort would be the last.
Linguists said it was a "major concern" and symptomatic of the decline of German across the country, which has been usurped in popularity by Spanish.
Between the 1960s and 1990s, hundreds of German troops and their families were stationed in Pembrokeshire while training in Castlemartin, leading to a growth in the number of secondary schools teaching the language.
Gareth Mills, Pembrokeshire council's head of learning partnerships said its popularity had waned over the past decade.
"We have seen a huge fall-off in the demand from parents and students for German," he said.
"We are only getting single figures coming through, so unfortunately it's no longer viable.
"It's very disappointing, but if the demand was there we would certainly put it back on."
Although three schools in Pembrokeshire will still teach German at GCSE, none of the county's further education colleges offer the subject at A- level.
In an effort to attract more learners, Sir Thomas Picton School in Haverfordwest has replaced its A-level course with an NVQ.
Although few schools with sixth-forms teach German A-level, the subject is on most 14-19 learning network option menus because it is offered at FE colleges.
Figures from the WJEC exam board show that entries for A-level German fell by 14 per cent last year. Spanish has overtaken German to become the second most popular foreign language studied at both A-level and GCSE.
Ceri James, director of Cilt Cymru, the national centre for languages, said German was suffering from being "untrendy", but was still important.
"If you look at multilingual job adverts, German is still very much in demand in the world of international business, manufacturing and export," he said.
Cilt Cymru programme manager Kristina Hedges said: "It's a major concern that German is disappearing from our schools.
"Welsh companies still need German speakers and if they can't find them here they will go elsewhere for them."
According to the General Teaching Council for Wales, since 2007 the number of German-trained teachers has fallen from 112 to 104.
Last year the Assembly government launched its long-awaited modern foreign languages (MFL) strategy, Making Languages Count, which is designed to improve language learning and teaching.