She was arrested in the early hours of Tuesday morning at the Adolfo Suarez Madrid–Barajas Airport as she attempted to board a flight to Turkey.
The 22-year-old resident of Almonte in southern Spain's Huelva province had converted to Islam and been radicalized, according to a statement from Spain's Interior Ministry.
La joven detenida esta madrugada en Barajas es española, tiene 22 años y se había convertido a la corriente más extrema del Islam— Ministerio Interior (@interiorgob) October 20, 2015
Work carried out by a specialist unit of the Civil Guard which monitors jihadist forums on the internet led to the arrest, the statement said.
“Investigations revealed that the person arrested had planned to travel to Turkey and then into Syria to join the ranks of Daesh,” said the statement referring to the Arabic name for the group also known as Isis.
“The Civil Guard is carrying out different operations of this nature which have so far led to the prevention of several Spanish residents from joining DAESH, including some minors,” the statement said.
It is the latest in a series of arrests of suspected jihadists in Spain. Recent police operations have seen the detention of cells suspected of radicalizing and recruiting fighters to send to Syria and Iraq.
She was the latest of several suspected female sympathizers detained in Spain since last year over security concerns.
In September, police arrested an 18-year-old Moroccan woman accused of preparing to travel to Syria to join the group, and in July a woman was arrested in the Canary Islands accused of recruiting young girls and facilitating their passage to areas controlled by Isis.
Like other European nations, Spain has made clamping down on radicalized Islamist cells a priority, but it has been unable to stem the flow of people out of the country to join Isis in Syria and Iraq.
Spain estimates that around 100 nationals have joined jihadist fighters in the two countries, a lower number than those from Britain, France and Germany.
Spanish officials fear they may return to launch attacks on Spanish soil. In March 2004, Al-Qaeda-inspired bombers blew up four packed commuter trains in Madrid, killing 191 people.