Yellen has also highlighted "considerable uncertainty" surrounding the Fed's projections for economic growth.
Central bank watchers will be trying to read into Yellen's comments for indications of when the Fed may next start hiking interest rates. In her written testimony, the chair was keen to stress that the decision will be dependent on the economy data.
If the labour market improves more rapidly than the Federal Open Market Committee anticipates, that an interest rate hike may come sooner. Similarly, disappointing economic performance could push the process of normalising monetary policy back.
On the first quarter drop in GDP seen by the US, Yellen told members of the Senate Banking, Housing, and Urban Affairs Committee that she sees the decline as resulting from factors that are "transitory" and "understates the momentum in the economy". Those factors undoubtedly include the terrible weather endured by the US over the winter.
The Bureau of Economic Analysis (BEA) has revised down its estimate for first quarter growth twice, initially thinking that the US economy had grown at an annualised rate of 0.1 per cent in the first three months of 2014. In June the BEA knocked that estimate down to -2.9 per cent, the largest downwards revision to a first estimate made by the agency since 1976.
The Nasdaq took a small hit on the release of Yellen's testimony, but has since recovered. Other US indices - the S&P500 and Dow - were largely unscathed by the Fed chair's comments.