After graduating from the youth academy of Everton in 2009, Nsiala spent time on loan at Macclesfield Town and Accrington Stanley, before joining Accrington Stanley permanently in May 2012. Released by Accrington in January 2013, he spent a brief time with Vietnamese club TDCS Dong Thap, and Southport in January 2014, before joining Grimsby Town.
Nsiala was born in Kinshasa in 1992, but moved to Paris with his mother and four siblings when he was three years old. He and his family moved again in 2002, to Liverpool. He began his football career playing for youth side Kingsley United in Toxteth, and was recruited by Everton's youth academy in 2007.
Nsiala rose through the ranks of Everton's youth system, and featured for the reserve team from 2009 onwards. He was an unused substitute for the Everton first-team in a UEFA Europa League dead rubber against BATE Borisov on 17 December 2009.
On 8 October 2010, Nsiala joined League Two club Macclesfield Town for a one-month-long youth loan, and made his debut the following day in a 2–1 away defeat to Lincoln City. His loan at Macclesfield was extended by a further two months by "Silkmens" boss Gary Simpson, and he made 13 appearances and scored one goal during his stay at Moss Rose. He scored his first goal in senior football on 16 November when he scored the opening goal of a 2–2 draw with Southport in the FA Cup.
He was an unused sub in the Premier League clash with Aston Villa at Goodison Park on 31 March 2011, and said that "[during] the last few minutes when I was told to get stripped off, I actually nearly wet myself!" In May 2011, he signed a new one-year contract with Everton.
Nsiala was loaned out to League Two club Accrington Stanley on 6 January 2012, signing an initial one-month loan deal, which was later extended until the end of the 2011–12 season.
Released by Everton, he signed for Paul Cook's Accrington Stanley in May 2012 on a one-year deal. He made twenty appearances for Accrington in the 2012–13 season, his contract was terminated by mutual consent on 10 January 2013 after he fell out of new manager Leam Richardson's first team plans.
He joined Torquay United on trial in July 2013, but failed to earn a contract. While on holiday, he played for Vietnamese club TDCS Dong Thap in the V.League 2.
Nsiala signed for Southport in January 2014, in a move that reunited him with John Coleman, his former manager at Accrington. He scored his first goal for the "Sandgrounders" on 15 March, in a 4–1 win over former club Macclesfield Town at Haig Avenue. He ended the 2013–14 season with 19 appearances to his name, helping Southport to finish two points above the relegation zone.
On 12 June 2014, Nsiala signed for Conference Premier side Grimsby Town on a one-year contract. He made his debut in the 0–0 stalemate to Bristol Rovers on the opening day of the season. He missed just six league games of the 2014–15 season as Paul Hurst's "Mariners" came 3rd in the Conference, and secured a play-off spot. Following an hamstring injury to Josh Gowling, Nsiala reverted to his favored centre-back position in the 2015 Conference Premier play-off Final against Bristol Rovers at Wembley on 17 May 2015; following a 1–1 draw after extra time, Grimsby lost 5–3 in a penalty shoot-out.
On 3 June 2015, Nsiala agreed a new one-year deal with the club. Nsiala's first goal for the club came on 11 August 2015 in the second game of the 2015–16 season, scoring the 4th goal in 4–1 thrashing of Barrow, a scramble in the box and Nsiala dived into a challenge to flick it home.
Nsiala played in Grimsby's 3–1 victory over Forest Green Rovers in the 2016 National League play-off Final at Wembley, seeing Grimsby promoted to League Two after a six-year absence from the Football League.
Nsiala joined Hartlepool United in June 2016 on a two-year deal, having turned down a new contract at Grimsby Town. Nsiala scored his first goal for the club in a 2–1 loss to Notts County on 20 August 2016. A week later he was sent off for deliberate handball in a 2–2 draw with Newport County. Nsiala was sent off again on 31 August 2016 in an EFL Trophy tie against Notts County, though this time it was expected to be a case of mistaken identity.
Six months into his contract at Hartlepool, Nsiala joined League One side Shrewsbury Town for an undisclosed fee on 1 January 2017, signing a deal until summer 2019. The move reunited him with Paul Hurst who had previously managed him at Grimsby. He was sent off 53 minutes into his Shrewsbury debut, having been deemed to have fouled Luke Norris in a 1−1 draw away at Swindon Town, although the red card was later rescinded on appeal. Nsiala scored his first goal for the club - a 90th minute match-winning header against AFC Wimbledon - on 18 February to earn his side a fourth successive home victory. In his first half-season he established a strong defensive partnership with the experienced left-sided centre-back Mat Sadler to help steer Shrewsbury away from relegation danger.
Eligible to play for DR Congo, England, Scotland and Wales, Nsiala was first called up by Wales to their under-19 training squad in July 2009.
He made his international debut for DR Congo in a qualifier for the 2013 Africa Cup of Nations against the Seychelles on 15 June 2012, coming on as a substitute for Diego Kazadi Mutombo in a 3–0 victory.As of match played on 16 September 2017.