*Club domestic league appearances and goals, correct as of 11 September 2023 ‡ National team caps and goals, correct as of 19:02, 11 October 2021 (UTC)
Sotiriou was born in Nicosia, Cyprus. He is a product of Olympiakos Nicosia academies. He made his official debut with Olympiakos in the 2009–10 season, when the club was competing in the Cypriot Second Division, appearing in four matches and scoring one goal. On 19 March 2011, he made his Cypriot First Division debut, playing the last 11 minutes in a match against Doxa Katokopias and he added a further five appearances in the 2010–11 season. The next season (2011–12), he made 16 league appearances (2 at starting line-up, 14 as a substitute) and scored his first Cypriot First Division goal on 18 September 2011, in the third matchday against APOEL where Olympiakos lost by 1–4. In June 2012, it was rumoured that Sheffield Wednesday[2] was interested in him and also on 5 August 2012, he was trialled at S.L. Benfica,[3] but finally stayed at Olympiakos. On 16 November 2012, he renewed his contract with Olympiakos, signing a three-year contract extension.[4] His most productive season with Olympiakos came in 2012–13, when he appeared in 29 league matches (28 at starting line-up, 1 as a substitute) and scored 8 goals.
At the end of the 2012–13 season, he has been awarded the "Young player of the season" award by Cyprus Football Association.
APOEL
On 24 December 2012, it was announced that Sotiriou's transfer from Olympiakos to APOEL FC was already agreed by the two clubs (for a transfer fee of €90,000), but he stayed to Olympiakos until the end of the 2012–13 season and his four-year contract with APOEL activated in June 2013.[5]
He scored his first official goal for APOEL on 20 September 2014, netting the second goal in APOEL's 3–1 away victory against Ayia Napa in the Cypriot First Division.[13] On 10 December 2014, he made his first group stage appearance, coming on as a 65th-minute substitute in APOEL's 4–0 defeat against Ajax at Amsterdam Arena.[14] On 15 December 2014, he scored twice in APOEL's enthralling 4–4 home draw against AEK Larnaca in the First Division.[15] In the 2014–15 season, he managed to add two more titles to his collection, as APOEL won again both the Cypriot championship and the 2014–15 Cypriot Cup.[16]
On 28 April 2016, Sotiriou scored the opening goal against title rivals AEK Larnaca and sealed the victory which secured APOEL's fourth consecutive Cypriot First Division title.[17]
On 19 September 2016, Sotiriou signed a three-year contract extension with APOEL, running until 31 May 2020.[20]
On 29 September, he scored the only goal in APOEL's 1–0 away victory against Greek club Olympiacos in the Europa League group stage.[21] On 3 November 2016, he scored again in the group stage in APOEL's 1–0 home victory against Swiss side BSC Young Boys.[22] He scored his first ever hat-trick on 8 January 2017, in APOEL's 5–0 home win against Aris Limassol in the 2016–17 First Division.[23][24] On 23 February 2017, he scored with a flying volley against Athletic Bilbao, as APOEL won 2–0 at home and overturned the 3–2 deficit from the first leg to advanced to the last 16 of the Europa League for the first time in their history.[25] Following his successful 2016–17 season with APOEL, Sotiriou awarded the "Player of the season" award by Cyprus Football Association.[26]
FC Copenhagen
On 25 April 2017, it was announced that FC Copenhagen had secured his signature on a five-year contract running from 1 July 2017, for an undisclosed transfer fee from APOEL, reported to be around €2.5 million.[27][28]
Astana
On 20 February 2020, FC Astana announced the signing of Sotiriou on a three-year contract.[29] The transfer fee paid to Copenhagen was reported as DKK37 million (about €5 million, £4 million).[30][31]
Ludogorets Razgrad
In February 2021, Sotiriou moved to Bulgarian club Ludogorets Razgrad on a three-and-a-half-year deal.[32][33]
Sanfrecce Hiroshima
On 15 August 2022, Sotiriou signed to J1 club, Sanfrecce Hiroshima for during mid season in 2022.[34] Also, in the Levain Cup final of the same year, he scored a tie goal and a come from behind goal and was awarded the MVP, contributing greatly to the team's victory in the Levain Cup.
On 28 December 2019 Sotiriou married with Cypriot journalist Maria Kortzia, after eight years of relationship. They have two sons: Sophocles (born 9 December 2020) and Giorgos (born 14 June 2022).
^Και ο Πιέρος στην Εθνική [Pieros at national team] (in Greek). kerkida.net. 9 October 2012. Archived from the original on 30 November 2012. Retrieved 14 December 2012.