[5] On 30 October 2008, Castaignos signed his first professional contract with Feyenoord, keeping him at De Kuip until summer 2011 with an option for another two seasons.

[9] After a successful performance with the Netherlands U17 at the 2009 UEFA European Under-17 Football Championship, a clutch of sides were linked to the Dutch youngster.

Besides Arsenal, also Liverpool, Manchester United, Real Madrid, Inter Milan, Bayern Munich and TSG 1899 Hoffenheim showed their interest in the Feyenoord's top scorer.

[10] However, on 22 July 2009, Castaignos crushed all rumours and told Feyenoord manager Mario Been and technical advisor Leo Beenhakker that he wanted to stay in Rotterdam.

[13] Castaignos made his official debut in Feyenoord's first team on 24 September 2009 replacing Leroy Fer in the 72nd minute in the KNVB Cup away match against Harkemase Boys and helped the club win 5–0.

[17] A month later on 24 March 2010, he made his first start of the season against FC Twente in the second leg of the KNVB Cup semi–finals and helped the club win 2–1 to reach the final.

[21] Following the club's elimination in the UEFA Europa League, Castaignos scored his first career goal for Feyenoord, in a 4–0 win against Vitesse on 28 August 2010.

[24] Amid to the contract rejection, he scored three goals in three matches between 31 October 2010 and 14 November 2010 against AZ Alkmaar, Roda JC and SC Heerenveen.

[26] Castaignos later scored two more goals by the end of the year, coming against ADO Den Haag on 28 November 2010 and SBV Excelsior on 11 December 2010.

[27] In a friendly match against Sparta Rotterdam on 5 January 2011, he received a straight red card in the 57th minute for kicking an opponent, in a 4–2 win.

[36] As a result of rejecting a new contract with Feyenoord, Castaignos was on the rampant speculation during the January transfer window, with Italian giants Inter Milan, PSV Eindhoven, Tottenham Hotspur and Valencia were interested in signing the player.

[38] After months of agreement, it was finally announced on 4 March 2011 by Feyenoord that the club had agreed to terms with Inter Milan, selling the player for a fee believed to be around €3 million upon the completions of the 2010–2011 season.

[43] This led the club's chairman Massimo Moratti commenting on the situation on the player, saying: "I was very sorry for Castaignos because he is a great guy, if this story came up he would play him.

[46] Castaignos then scored his first goal in Serie A in an away match to Siena on 27 November 2011, latching on to Thiago Motta's through ball before firing low past Brkić, which proved to be the game winner.

[64] Since joining FC Twente, Castaignos quickly established himself as the club's first choice striker and was living up to his potential as De Jong's successor.

[67] In a match against FC Den Bosch in the third round of the KNVB Cup on 30 October 2012, Castaignos set up the club's only goal of the game, but was sent–off for a second bookable offence, in a 2–1 loss.

[83] After serving a one match suspension, Castaignos made his return to the starting line–up against Ajax on 30 March 2014 and played 70 minutes before being substituted, in a 3–0 loss.

[85] After serving a two match suspension, Castaignos returned to the starting line–up against NEC Nijmegen on 27 April 2014 and helped FC Twente qualify for the UEFA Europa League next season.

[111] After a promising start at the club, Castaignos' performance was criticised due to not scoring regularly and was demoted to the substitute bench as a result.

[113] However, Castaignos suffered ankle injury during a match against Bayer Leverkusen on 21 November 2015 and was substituted in the 22nd minute, as Eintracht Frankfurt lost 3–1.

[122] In summer 2016, Castaignos joined compatriot Bas Dost at Portuguese side Sporting CP on a three-year deal.

[133] Amid the transfer speculation, Castaignos made his appearance for Sporting CP in over a year, coming on as a late substitute, in a 1–1 draw against rivals, Benfica on 25 August 2018.

[137] It was announced on 19 February 2019 that Castaignos left Sporting CP by mutual consent after months of speculation over his future at the club.

[142] Since joining Vitesse, Castaignos found his playing time, coming on from the substitute bench and competed with Tim Matavž over the first choice striker role.

[146] After missing one match, Castaignos returned to the first team from injury, coming on as an 83rd-minute substitute, in a 4–2 loss against FC Groningen on 19 November 2017.

[147] Three weeks later on 7 December 2017, he scored his second goal for Vitesse, in a 1–0 win against OGC Nice in the UEFA Europa League Group Stage.

[149] He played in both legs of the play-off against FC Utrecht and helped Vitesse win 5–3 on aggregate to qualify for the UEFA Europa League next season.

[190] Castaignos' international fame started to rise after the 2009 UEFA European Under-17 Football Championship in Germany and was called up to the Netherlands U17 squad for the FIFA U-17 World Cup in Nigeria.

[205] Castaignos made his U20 national team debut, starting a match and played 70 minutes before being substituted, in a 3–0 win against Denmark U21 on 29 February 2012.

[225] In March 2011, Castaignos and his then teammate Ron Vlaar took part in a spinning marathon for the charity, Stichting Luna Sluiter Foundation.