Bring a pot of lightly salted water to a boil. Add snap peas; cook 1 to 2 minutes, until crisp-tender. Drain snap peas; run under cold water until cool.
In a large bowl, whisk together oil, vinegar, tarragon and salt until well combined. Toss snap peas and radishes in dressing. Season with freshly cracked pepper. Serve at room temperature or chilled.