In December 1936 the Fal-led Junta Nacional Carlista de Guerra, the war-time party executive, nominated Tellería one of 2 “inspectores jefe de servicio”, part of the infrastructure supposed to launch the Carlist-only Real Academia Militar de Requetés.
He resumed also his pre-war position of the provincial Gipuzkoan party leader.
The family Antzuola factory was now working for the Nationalist war machine and in early 1937 he published account of his days in the Republican zone as a booklet, El milagro de Agustín Tellería.
De miliciano rojo a soldado de la España Imperial.
In March 1937 the Republican court in Bilbao in course of formal proceedings declared Tellería guilty of rebellion and sentenced him to prison; the same ruling was applied to his son, one month earlier killed in action.

Tellería’s position towards mounting Franco’s pressure for Carlist unification with Falange is not entirely clear.
One scholar classified him as “carlista posibilista”.
However, in late March 1937, during heated internal debates within Carlism, Tellería seemed to side with the intransigent Falcondistas.
In course of one of key meetings in Burgos he questioned the legality of Consejo de la Tradición, a body formed by the Rodeznistas as part of their strategy to overpower Fal.
Shortly after declaration of the forced unification and watching a joint Carlist-Falangist juvenile parade in San Sebastián, he remarked: “this is shameful.
This is intolerable.
What is this all about?
Tomorrow I go to Salamanca to speak to Rodezno”.
He did, and returned excited; he got convinced that the arrested Hedilla conspired against Franco, that with marginalisation of Falange “the moment is ours, entirely ours”, and that the Carlists should seize it and align with the military.
This is what he wholeheartedly recommended to the regent, Don Javier.

In late April 1937 Tellería was nominated the first provincial Gipuzkoan jefe of the unified Falange Española Tradicionalista.
At this role he tried to ignore the Falangists, to pay due respect to the army and to advance Traditionalism as the political cause; when leading preparations to the first anniversary of Nationalist troops taking San Sebastián, he tried to format the gala as an exalted Carlist spectacle.
Since alarm signals were sent to Burgos, an “inspector nacional” and “inspector general” of FET arrived at San Sebastián and investigated; in early September Tellería was promptly dismissed, before the anniversary celebrations took place.
However, Tellería did not fall out of grace entirely.
In October he was allowed a radio speech, already as ex-delegado, and in early 1938 he was confirmed by the military as “inspector de las comisarías de Requetés, now formally under the army command.
Little is known of activity at this role.
On March 20, 1939 he lost control over his car on a slippery, poorly maintained road in Betoño, near Vitoria; he survived the crash, but perished the following day in a hospital.
The funeral was attended by Rodezno, civil and military governors, president of the Alavese diputación and the mayor of San Sebastián.
In December 1936 the Fal-led Junta Nacional Carlista de Guerra, the war-time party executive, nominated Tellería one of 2 “inspectores jefe de servicio”, part of the infrastructure supposed to launch the Carlist-only Real Academia Militar de Requetés. He resumed also his pre-war position of the provincial Gipuzkoan party leader. The family Antzuola factory was now working for the Nationalist war machine and in early 1937 he published account of his days in the Republican zone as a booklet, El milagro de Agustín Tellería. De miliciano rojo a soldado de la España Imperial. In March 1937 the Republican court in Bilbao in course of formal proceedings declared Tellería guilty of rebellion and sentenced him to prison; the same ruling was applied to his son, one month earlier killed in action. 
Tellería’s position towards mounting Franco’s pressure for Carlist unification with Falange is not entirely clear. One scholar classified him as “carlista posibilista”. However, in late March 1937, during heated internal debates within Carlism, Tellería seemed to side with the intransigent Falcondistas. In course of one of key meetings in Burgos he questioned the legality of Consejo de la Tradición, a body formed by the Rodeznistas as part of their strategy to overpower Fal. Shortly after declaration of the forced unification and watching a joint Carlist-Falangist juvenile parade in San Sebastián, he remarked: “this is shameful. This is intolerable. What is this all about? Tomorrow I go to Salamanca to speak to Rodezno”. He did, and returned excited; he got convinced that the arrested Hedilla conspired against Franco, that with marginalisation of Falange “the moment is ours, entirely ours”, and that the Carlists should seize it and align with the military. This is what he wholeheartedly recommended to the regent, Don Javier.
In late April 1937 Tellería was nominated the first provincial Gipuzkoan jefe of the unified Falange Española Tradicionalista. At this role he tried to ignore the Falangists, to pay due respect to the army and to advance Traditionalism as the political cause; when leading preparations to the first anniversary of Nationalist troops taking San Sebastián, he tried to format the gala as an exalted Carlist spectacle. Since alarm signals were sent to Burgos, an “inspector nacional” and “inspector general” of FET arrived at San Sebastián and investigated; in early September Tellería was promptly dismissed, before the anniversary celebrations took place. However, Tellería did not fall out of grace entirely. In October he was allowed a radio speech, already as ex-delegado, and in early 1938 he was confirmed by the military as “inspector de las comisarías de Requetés, now formally under the army command. Little is known of activity at this role. On March 20, 1939 he lost control over his car on a slippery, poorly maintained road in Betoño, near Vitoria; he survived the crash, but perished the following day in a hospital. The funeral was attended by Rodezno, civil and military governors, president of the Alavese diputación and the mayor of San Sebastián.
Agustín Tellería Mendizábal