[3] In the 1996–97 season, under Lettieri, Bayern Hof got two wins, one draw, and three losses[4] to finish 15th in the Bayernliga.
[37] During the 2010–11 season, Wehen Wiesbaden narrowly missed out on the promotion playoff by a single point.
[38] Wehen Wiesbaden started the 2011–12 season with a 2–1 win against Werder Bremen II on 23 July 2011.
[39] On 15 February 2012 with the club dangerously hanging round the relegation zone, SV Wehen sacked him,[40] and replaced him with Peter Vollmann the next day.
FC Köln in the second round of the German Cup on penalties after the match had finished in a 0–0 draw.
[51] Lettieri was relieved of his duties on 2 November 2015, his final match was a 1–0 loss to 1860 Munich.
[54] On 7 March 2017, he was appointed as the new manager of FSV Frankfurt als a successor to Roland Vrabec.
[55] He received a contract until the end of the 2016–17 season and was tasked with preventing the club's relegation from the 3.
Since this goal was not achieved and FSV Frankfurt got relegated, he left the club the end of the season.
[57] In September 2019, Lettieri was sacked by Kielce after the team lost four games in a row.
[58] Lettieri returned to MSV Duisburg on 11 November 2020 as the successor of Torsten Lieberknecht.
[60][61] In October 2021, he joined Greek club AEK as an assistant under head coach Argiris Giannikis.
[62] In September 2022, Lettieri was appointed as the new coach of Lithuanian club FK Panevėžys, replacing Valdas Urbonas.