The widely-watched investor confidence index calculated by the ZEW economic institute jumped by 23.4 points in December, after rising for the first time this year in November, ZEW said in a statement.
It said there was abundant evidence that faith in Europe's top economy among financial market experts was being restored.
"This renewed confidence remains linked to the auspicious economic conditions including the weak euro and the low price of oil," ZEW president Clemens Fuest said in a statement.
”This positive trend could be seen in the recent data for German exports. But it should be noted that the current economic optimism is fostered by factors that can change quickly."
For its survey, ZEW questions analysts and institutional investors about their current assessment of the economic situation in Germany, as well as their expectations for the coming months.
The sub-index measuring financial market players' view of the current economic situation in Germany also rose, by 6.7 points.
In November the ZEW headline indicator had bounced back for the first time in 2014, adding to signs that the German economy is stabilising and providing a boost for the eurozone as a whole.
After hitting a 22-month low in October, the index jumped to 11.5 points from minus 3.6 points the previous month.
Last week Germany reported that its trade surplus had grown slightly in October, with imports showing a sharper decline than exports due in part to the weaker euro.
Exports slipped by 0.5 percent in October to €97.2 billion compared to the previous month, while imports fell 3.1 percent to €76.6 billion, according to seasonally adjusted figures published by the federal statistics office Destatis.