The terms include a cash payment of €6.5 million and an additional, performance-based payment of up to €4.5 million.
Hamburg-based Lademannbogen is expected to have revenue for the 2009 calendar year of about €20 million.
The acquisition is conditional upon approval from German anti-trust authorities.
"Joining forces with the Lademannbogen laboratory is a positive and attractive progression for Sonic Healthcare in Germany,'' Sonic chief executive Colin Goldschmidt said.
"With our well-established presence in the northern German market, the highly respected and like-minded Lademannbogen laboratory fits with our ongoing growth strategy and will add value to Sonic at operational and technical levels.
"With the potential for significant synergy in one of Germany's largest metropolitan areas, this acquisition further underlines our commitment to the German laboratory market.''
In November last year, Sonic issued new shares to raise $425 million and said it would have about $475 million available for acquisitions.
Sonic already has three operations in Germany: Bioscientia, Labor 28 and GLP Medical.
Sonic shares were 5 cents higher at $11.46 at 10.41am (AEST).
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