The club revealed the news of the former Manchetser City forward's acquisition via their official twitter page, before releasing a statement on their website.
"CONFIRMED The club has agreed a deal with @valenciacf to bring @AlvaroNegredo_7 to #Boro -," the tweet read.
According to the club's website, Negredo 'is set to join on a season-long loan once all the paperwork is complete.'
The 30-year-old brings a wealth of experience, having netted 112 La Liga goals in 264 appearances, as well as having the benefit of having previously competed in the English Premier League.
City secured his services for £16.4m from Sevilla FC in the summer of 2013 and he subsequently went on to score 23 goals in 48 appearances, which included a Champions League hat-trick.