Aris 2011–12 season Born in Neochori, Greece, Gianniotas started his career in youth teams of Aris. In 2011, new head coach
Michał Probierz promoted him to the first team, and he made his debut on 5 November 2011, in a game against
Olympiacos. He scored his first goal for Aris only during his second appearance for the team, in a game against
OFI. For that performance, he was named
MVP of matchday 10 in the
Greek Super League. He scored another goal against Levadeiakos, and this one was named the best for the matchday 4. He also scored against
Panetolikos in a 5–1 away loss. In total he scored three goals and he made 19 appearances.
2012–13 season His first goal for this season came against
Panathinaikos in a 1–1 away draw. His next goal came against
PAS Giannina in a 1–2 home loss. He also scored against
Asteras Tripolis in a 1–1 away draw. He managed to score in a Greek Cup match against
Kallithea in a 3–1 away loss.
Fortuna Düsseldorf In June 2013, he was transferred to
Fortuna Düsseldorf. His previous club
Aris received 450,000 euros for the transfer. He chose the jersey with the number "22" on the back, and signed a contract until 2016.
"The people of Fortuna are keen for this transfer, I came to a great club with a great stadium", said the former Aris forward.
"I always wanted to play in Germany," he said and concluded:
"I hope that I can help Fortuna Düsseldorf to return in Bundesliga". On 30 August 2014 the Rhinelander agreed with the Greek first division Asteras Tripolis on a lending transaction until 30 June 2015.
Asteras Tripolis On 22 March 2015 after a remarkable season with the club, Giannis Gianniotas became the 1st player of Asteras Tripolis that was called to play for the
Greece national team. On 23 March 2015, Gianotas alleged to have verbally agreed to Greek champions
Olympiacos and seems that
Fortuna Düsseldorf which has the player's rights contents to this transfer. Giannotas has another year contract with the German club.
Fortuna Düsseldorf, which is trying for a rise to
Bundesliga has no problem to release the Greek footballer, without being known if will claim an amount for transcription. It is noted that the situation should be clarified in the coming days. On 5 June 2015,
Olympiacos reached an agreement with
Fortuna Düsseldorf for the transfer of Giannis Gianniotas. The Greek international signed a 4-year contract worth €400,000 per year with the Greek champions, that will be pay
Fortuna Düsseldorf €500,000 as a transfer fee.
Olympiacos On 17 June,
Olympiacos officially announced the transfer of Giannis Gianniotas from
Fortuna Düsseldorf, adding another high-caliber Greek talent to their squad.
APOEL On 31 December 2015, Gianniotas joined Cypriot club
APOEL on a six-months loan deal, until the end of the
2015–16 season. He made his debut on 10 January 2016, starting the match and playing for 65 minutes in APOEL's 2–1 away victory against
Aris Limassol for the
Cypriot First Division. He scored his first official goal for APOEL on 17 January 2016, in his team's 3–0 home win against
Enosis Neon Paralimni for the
Cypriot First Division. On 28 April 2016, Gianniotas scored with a penalty kick against title rivals
AEK Larnaca, and sealed the victory which secured his team's fourth consecutive
Cypriot First Division title and the first title of his career. On 12 July 2016, APOEL agreed with Olympiacos to extend Gianniotas loan for one more year, until the end of the 2016–17 season. On 2 August 2016, he scored the opening goal in APOEL's 3–0 home victory against
Rosenborg BK for the
third qualifying round of the
UEFA Champions League, to help his team overturn a 2–1 loss in Norway and reach the
play-off round of the competition. On 16 February 2017, he scored APOEL's second goal one minute before the end, in his team's 3–2 defeat from
Athletic Bilbao at
San Mamés, for the first leg of the
UEFA Europa League round of 32. One week later, he scored again from the
penalty spot, as APOEL beat
Athletic Bilbao 2–0 at home and advanced to the
last 16 of the
UEFA Europa League for the first time in their history.
Real Valladolid On 25 August 2017 Gianniotas joined
Real Valladolid on a season-long loan. On 16 September 2017, in his debut with the club he scored with a right footed shot from the centre of the box to the bottom right corner, after an assist from
Míchel, giving a lead of two goals in a 2–1 home win game against
Granada. On 12 October 2017, just a couple of days after his international goal against
Gilbraltar, few minutes after his entrance in the match, Gianniotas left his imprint with a solo goal, which sealed a 4–0 home win against
Alcorcón. According to reports from Spain, Real Valladolid after Gianniotas solid performances with the club want to make the loan move of right winger from
Olympiacos permanent in the summer. The current contract of 25-year-old international winger with the Reds expires in the summer of 2019 and it will not be extended. He had an excellent season, helping the club to be promoted in
La Liga.
AEK Athens On 29 August 2018, Gianniotas joined
AEK Athens as a free transfer on a three-year contract for an undisclosed fee. On 31 October 2018,
Alef calmly slid the ball into the left corner after collecting
Stratos Svarnas’ accurate pass and Gianniotas’ scored his first goal with the club, to double AEK’s lead in a 4–0 away
Greek Cup win.
Apollon Limassol On 27 June 2019,
Apollon Limassol signed him for the next two years and caught all the Greeks clubs that had expressed interest along with
Aris and
Atromitos.
Apollon Smyrnis On 4 January 2022, Greek side
Apollon Smyrnis, via his official website, informed about the acquisition of Giannotas from
Apollon Limassol on a free transfer. The winger, after passing the medical tests, signed a contract with the Greek club valid until June 30, 2023.
Levadiakos On 30 September 2022, Gianniotas joined
Levadiakos.
Aris On 25 June 2025, Gianniotas joined again
Aris. ==International career==