An apparatus for estimating bio-information includes: a sensor configured to obtain a bio-signal from an object; and a processor configured to obtain a second-order differential signal of the bio-signal, to detect at least one of an inflection point in a predetermined period of the second-order differential signal, and a zero-crossing point in the predetermined period of the second-order differential signal, to extract a feature based on the detected at least one of the inflection point and the zero-crossing point, and to estimate bio-information based on the extracted feature.