The Italian popped up to slot home in the 71st minute as Inter earned a hard-fought UEFA Europa League win against 10 men in Kiev on their 350th European appearance.
The win came as a relief to the Italians in a game where Dnipro appeared to have the measure of their visitors until captain Ruslan Rotan picked up his second yellow card midway through the second half.
And D'Ambrosio was clearly delighted with his own contribution as Inter, fresh from a 7-0 Serie A triumph over Sassuolo, continued their unbeaten start to the campaign in all competitions.
He told Mediaset Premium: "It was important to play a great game and prove our triumph against Sassuolo on Sunday was not a fluke.
"It's the most important goal of my career and my first in Europe."
Despite his euphoria, the 26-year old insists his side remain focused on continuing their impressive start with a win against Palermo in the league on Sunday.
He added: "Having won this game, we now have to look forward and think about Palermo, as that will be a very difficult challenge."
Boss Walter Mazzarri echoed the Italian's sentiments, claiming his side were worthy winners in Ukraine, while also hinting there could be more to come from his team.
He told La Presse: "We knew it would be tough and that we would not be given space. We set the pace in a certain way and even had some younger players making their European debut.
"I was pleased to play a good game, because we have changed heavily in training and this proof that we have a good squad."
The result leaves Inter top Group F, with Saint-Etienne held to a 0-0 draw by Azerbaijani outfit Qurabag, and Mazzarri's men will undoubtedly fancy their chances of emerging as pool winners.