De Guindos has served as economy minister since Mariano Rajoy's center-right government took power at the end of 2011. Shortly afterwards, the country requested international aid for its banks, which were crippled by piles of non-performing real estate loans.
Spain received a loan of around $100 billion for its lenders, which de Guindos helped negotiate, as well as helping push through reforms of the country's banks and labor markets.
The Spanish economy returned to growth at the start of 2014, having exited its bailout at the start of the year. The economy accelerated further in 2015 to grow by 3.2 percent.
De Guindos said Spain's experience showed it was best to make reforms as soon as possible and that "the first reforms you have to implement are the hardest ones."
At the panel discussion in Washington D.C., IMF Deputy Managing Director Min Zhu added: "We observe in Europe that people more and more realize that structural reform is a must."
The rise in protest parties brought an end to Spain's traditional bi-party system in its elections in December 2015. Rajoy's People's Party won the most votes, but failed to gain an absolute majority, while the upstart anti-austerity party, Podemos, came a close third to the Socialist Workers' Party.