Born in Sanet y Negrals, Alicante, Valencian Community, Femenía was a product of Hércules CF's youth ranks. He made his first-team debut on 15 June 2008 at just 17, appearing in a Segunda División match at Cádiz CF, a 1–1 draw which eventually certified the Andalusians' relegation even though they protested against the illegal fielding of an opposing player, specifically the youngster. During the 2008–09 season, Femenía played another game with the main squad, again in the last round but against UD Salamanca. In the subsequent off-season, he signed his first professional contract after agreeing to a five-year deal and, in the following campaign, still only 18, he would be a much more important midfield unit, being the first substitute for veteran Francisco Rufete and appearing in nearly 1,000 minutes in the league to help the club return to La Liga after an absence of 13 years. On 28 August 2010, Femenía made his debut in the top division, replacing Abel Aguilar in the second half of the home fixture against Athletic Bilbao. After only a few minutes on the pitch, however, and a couple of poor decisions, he suffered an anxiety attack from which he later fully recovered, although the Basques eventually won it 1–0.
Barcelona
Femenía joined FC Barcelona B on 6 July 2011, for €2 million plus €1.5 million in add-ons. He scored his first official goal for his new team on 4 September, opening the score in a 4–0 away win against FC Cartagena. Femenía netted five times in 30 games – 23 starts – in his first season, helping the Catalans to the eighth position.
In late August 2013, Femenía was released by Barcelona, stating that he had been "ruined emotionally". Just hours later, he signed for Real Madrid, being assigned to the reserves in the second level. Femenía appeared in only five matches during the whole campaign, which ended in relegation, and left the club in December 2014.
Alcorcón
On 7 January 2015, Femenía signed a six-month deal with AD Alcorcón also of the second tier. He totalled 996 minutes of action during the season, helping his team finish 11th.
Alavés
On 2 July 2015, Femenía moved to fellow league side Deportivo Alavés after agreeing to a one-year contract. He contributed with 38 appearances and five goals in his debut campaign as they returned to the top flight after ten years, and was eventually reconverted into a right back. Femenía left the club on 6 June 2017, as his contract was due to expire.
Watford
On 1 July 2017, Femenía signed for Watford after agreeing to a four-year deal. He made his debut in the Premier League on 12 August, coming on for injured Daryl Janmaat early into a 3–3 home draw against Liverpool. Femenía scored his first league goal for the English club on 31 March 2018, helping the hosts earn one point after a 2–2 home draw to Bournemouth.
