Hard-working, tenacious, attacking midfielder Shelvey was one of Rafa Benítez’ last signings at Liverpool. When Shelvey was only 16 years and 59 days old he became Charlton Athletic's youngest-ever player when featuring for the Addicks against Barnsley in the Championship on 26 April 2008. A year later Chelsea came calling but by rejecting the London Blues, the young East Londoner had obviously thought carefully about a career path that would give him the best chance of success. He stayed loyal to the first club that had offered him a professional contract, Charlton Athletic. Shelvey made 49 appearances for the London club, scoring eight goals before accepting a move to Liverpool two years later. The Reds paid an initial £1.7m with further potential payments up to £3m depending on domestic and international appearances.

If it was unsettling that Rafa, who had signed him, left so soon after his own arrival at Anfield, it soon became clear that incoming boss Roy Hodgson was already aware of the midfielder’s promise. Still a teenager when his debut season as a Liverpool player finished, Shelvey could look back on 21 first-team appearances, but he only made four starts. Shelvey joined Championship side Blackpool on loan at the end of September until 31 December 2011, but returned home a month earlier the day after Lucas Leiva was stretchered off in Liverpool's League Cup quarter-final at Stamford Bridge. Shelvey had tremendous success at Blackpool, scoring six goals in ten Championship matches, including a hat-trick in a 5-0 victory at Leeds. He made nine starts in 2011/12 and could be happy with his progress although he didn't feature in either cup final. The run of matches he had in the second half of the season must have done wonders for his confidence. In the final home match of the season, he scored his first Premier League goal with a blistering shot from distance that flew past Chelsea goalkeeper Ross Turnbull like a guided missile. In the second week of July 2012, Jonjo signed a new long-term contract. "Tactically I have become a lot better and technically too," Shelvey said. "When you're working with people like Steven Gerrard and people like that, you're learning things day in, day out and it's an honour."

Shelvey had an impressive start to 2012/13, which included three goals in two Europa League matches, scoring home and away against Young Boys of Bern and also opening the scoring in the home defeat by Udinese. Shelvey earned a call-up to England's senior squad for the first time for the October World Cup qualifying matches against San Marino and Poland. He made his full international debut when coming on as a second-half substitute for Michael Carrick in the first of those two matches, against the group minnows at Wembley. Shelvey appeared in just under 60% of Liverpool's competitive matches in 2012/13, a season in which he celebrated his 21st birthday. But he only started three matches in the second half of the season and was an unused substitute almost as many times as he actually played from the start. Shelvey did lack composure and concentration when involved in the heat of battle in midfield. Rodgers felt he did not use the opportunities given and he was sold to Swansea in the summer of 2013. He became an integral part of their midfield and in September 2015 was called up to the England squad for the first time in three years. Shelvey was sold to Newcastle United in January 2016 for £12m of which Liverpool earned 10% of Swansea's £6m that they made on their sale. He was named captain on four occasions but he couldn't help Newcastle avoid the drop.

Despite relegation Shelvey remained with Newcastle for 2016/17. Apart from four games out suspended, he was an ever present and scored five times as they made an instant return to the top flight. 2017/18 saw him appear thirty times, scoring once. 2018/19 was a frustrating season in Tyneside for Shelvey, who struggled to force his way back into the side after picking up a thigh injury in November. He made only sixteen appearances in the league all season and in April 2019 was forced to deny rumours of a rift with manager Rafa Benitez, saying he had to accept others had seized their opportunity in his absence. In 2019/20, with Steve Bruce now manager, Shelvey featured more often and scored five times in 25 starts, nine of which he was captain. He stood in as captain on occasions again in 2020/21 when he started 29 times. He struggled with a calf injury at the start of 2021/22 but captain the side in the second half of the season. After missing the first two months of 2022/23 with a hamstring injury he struggled to get back in the side and joined Nottingham Forest in the January transfer window.

Shelvey was reportedly upset at being left out of the starting eleven for Forest's game at Anfield on 22nd April 2023. Although manage Steve Cooper said there was no problem between them he made no further appearances that season and was left out of the pre season training camp and not allocated a squad number for 2023/24. On 14th September 2023, a season long loan with Turkish side Çaykur Rizespor was agreed. It later transpired that this deal would exceed the FIFA imposed limit for players on loan, leading to Forest terminating his contract which was due to expire in 2024 anyway and making the move a free transfer. Shelvey had a good campaign in Turkey, missing only two games due to injury and suspension and captaining them on two occasions. Rizespor were unable to keep him on any longer for financial reasons and in August 2024 Shelvey joined Eyupsor, who had been promoted the Turkish top flight for the first time in their 105 year history. After just six appearances his contract was cancelled by mutual consent in January 2025 and he joined Burnley, who were pushing for promotion from the Championship. Shelvey only made two substitute appearances for Burnley as they were promoted to the Championship and started twice in the FA Cup. Shelvey joined Arabian Falcons in the second division of the United Arab Emirates on 28 September 2025.