The clubs have reached agreement on a deal reported at around €25 million for the 22-year-old Paraguay international, reuniting Enciso with the coach who oversaw his best form in Ligue 1 last season before O'Neil's move to Suffolk this summer.
It will be a second spell at Portman Road for Enciso, who spent six months on loan there from Brighton in 2025 before completing a permanent transfer to Strasbourg, a club that shares ownership with Chelsea through the BlueCo group.
Reports on the fee Strasbourg paid for him last year have varied, with figures ranging from around £10 million to as high as £13.8 million depending on the source; Strasbourg officials had believed at the time that Enciso had the potential to eventually earn a move to Stamford Bridge himself.
Although Ipswich Town's fee for the forward has not been officially disclosed, those involved in the deal believe it will account for a sizeable portion of the club's remaining transfer budget and deliver Strasbourg a substantial profit on what they paid last summer.
Enciso's arrival adds to what has already been an active window at Portman Road. Ipswich have made ten major signings so far, including Daizen Maeda from Celtic, Abdul Fatawu from Leicester City and club-record signing Emersonn from Toulouse, whose £24 million fee remains the benchmark this summer. It remains unclear whether the Enciso deal will surpass that figure once finalised. Having secured promotion from the Championship, Ipswich begin their Premier League campaign at home to Sunderland on 22 August.
Not every pursuit has gone as smoothly. Ipswich's bid for Bayer Leverkusen's World Cup-winning midfielder Exequiel Palacios has been turned down, according to reports, with the Bundesliga club standing firm on a valuation of around €35 million for the Argentina international.
Palacios is said to want a move to a bigger club, and Ipswich are understood to face competition from at least four other sides across the Premier League and Bundesliga for his signature.
The 27-year-old, who came through the ranks at River Plate before joining Leverkusen in 2020, made 18 Bundesliga appearances last season, starting 12 league matches and contributing one assist.